Add dawn_platform::Platform for handling tracing events in Dawn

This patch provides Chromium TRACE_EVENT macros and hooks for
implementing the TRACE_EVENT api.

Bug: chromium:958013
Change-Id: I033b1c7ca57c550504a1bea1898a1a152831922b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/7060
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

BUILD.gn

@@ -20,6 +20,25 @@ import("scripts/dawn_overrides_with_defaults.gni")
 
 import("//testing/test.gni")
 
+###############################################################################
+# dawn_platform
+###############################################################################
+
+source_set("dawn_platform") {
+  configs += [ "${dawn_root}/src/common:dawn_internal" ]
+
+  sources = [
+    "${dawn_root}/src/include/dawn_platform/DawnPlatform.h",
+    "src/dawn_platform/tracing/EventTracer.cpp",
+    "src/dawn_platform/tracing/EventTracer.h",
+    "src/dawn_platform/tracing/TraceEvent.h",
+  ]
+
+  deps = [
+    "${dawn_root}/src/common",
+  ]
+}
+
 ###############################################################################
 # libdawn_native
 ###############################################################################
@@ -98,7 +117,9 @@ source_set("libdawn_native_sources") {
   # Dependencies that are needed to compile libdawn_native entry points in
   # FooBackend.cpp need to be public deps so they are propagated to the
   # libdawn_native target
-  public_deps = []
+  public_deps = [
+    ":dawn_platform",
+  ]
 
   sources = get_target_outputs(":libdawn_native_utils_gen")
   sources += [

src/dawn_native/CommandEncoder.cpp

@@ -27,6 +27,7 @@
 #include "dawn_native/PassResourceUsageTracker.h"
 #include "dawn_native/RenderPassEncoder.h"
 #include "dawn_native/RenderPipeline.h"
+#include "dawn_platform/tracing/TraceEvent.h"
 
 #include <map>
 
@@ -667,6 +668,8 @@ namespace dawn_native {
     }
 
     CommandBufferBase* CommandEncoderBase::Finish(const CommandBufferDescriptor* descriptor) {
+        TRACE_EVENT0(GetDevice()->GetPlatform(), TRACE_DISABLED_BY_DEFAULT("gpu.dawn"),
+                     "CommandEncoderBase::Finish");
         if (GetDevice()->ConsumedError(ValidateFinish(descriptor))) {
             // Even if finish validation fails, it is now invalid to call any encoding commands on
             // this object, so we set its state to finished.

src/dawn_native/DawnNative.cpp

@@ -15,6 +15,7 @@
 #include "dawn_native/DawnNative.h"
 #include "dawn_native/Device.h"
 #include "dawn_native/Instance.h"
+#include "dawn_platform/DawnPlatform.h"
 
 // Contains the entry-points into dawn_native
 
@@ -120,6 +121,14 @@ namespace dawn_native {
         return mImpl->IsBeginCaptureOnStartupEnabled();
     }
 
+    void Instance::SetPlatform(dawn_platform::Platform* platform) {
+        mImpl->SetPlatform(platform);
+    }
+
+    dawn_platform::Platform* Instance::GetPlatform() const {
+        return mImpl->GetPlatform();
+    }
+
     size_t GetLazyClearCountForTesting(DawnDevice device) {
         dawn_native::DeviceBase* deviceBase = reinterpret_cast<dawn_native::DeviceBase*>(device);
         return deviceBase->GetLazyClearCountForTesting();

src/dawn_native/Device.cpp

@@ -112,6 +112,10 @@ namespace dawn_native {
         return mAdapter;
     }
 
+    dawn_platform::Platform* DeviceBase::GetPlatform() const {
+        return GetAdapter()->GetInstance()->GetPlatform();
+    }
+
     FenceSignalTracker* DeviceBase::GetFenceSignalTracker() const {
         return mFenceSignalTracker.get();
     }

src/dawn_native/Device.h

@@ -56,6 +56,7 @@ namespace dawn_native {
         MaybeError ValidateObject(const ObjectBase* object) const;
 
         AdapterBase* GetAdapter() const;
+        dawn_platform::Platform* GetPlatform() const;
 
         FenceSignalTracker* GetFenceSignalTracker() const;
 

src/dawn_native/Instance.cpp

@@ -192,4 +192,12 @@ namespace dawn_native {
         return mBeginCaptureOnStartup;
     }
 
+    void InstanceBase::SetPlatform(dawn_platform::Platform* platform) {
+        mPlatform = platform;
+    }
+
+    dawn_platform::Platform* InstanceBase::GetPlatform() const {
+        return mPlatform;
+    }
+
 }  // namespace dawn_native

src/dawn_native/Instance.h

@@ -63,6 +63,9 @@ namespace dawn_native {
         void EnableBeginCaptureOnStartup(bool beginCaptureOnStartup);
         bool IsBeginCaptureOnStartupEnabled() const;
 
+        void SetPlatform(dawn_platform::Platform* platform);
+        dawn_platform::Platform* GetPlatform() const;
+
       private:
         // Lazily creates connections to all backends that have been compiled.
         void EnsureBackendConnections();
@@ -78,6 +81,8 @@ namespace dawn_native {
         bool mEnableBackendValidation = false;
         bool mBeginCaptureOnStartup = false;
 
+        dawn_platform::Platform* mPlatform = nullptr;
+
         std::vector<std::unique_ptr<BackendConnection>> mBackends;
         std::vector<std::unique_ptr<AdapterBase>> mAdapters;
 

src/dawn_native/Queue.cpp

@@ -20,6 +20,7 @@
 #include "dawn_native/Fence.h"
 #include "dawn_native/FenceSignalTracker.h"
 #include "dawn_native/Texture.h"
+#include "dawn_platform/tracing/TraceEvent.h"
 
 namespace dawn_native {
 
@@ -29,6 +30,8 @@ namespace dawn_native {
     }
 
     void QueueBase::Submit(uint32_t commandCount, CommandBufferBase* const* commands) {
+        TRACE_EVENT0(GetDevice()->GetPlatform(), TRACE_DISABLED_BY_DEFAULT("gpu.dawn"),
+                     "Queue::Submit");
         if (GetDevice()->ConsumedError(ValidateSubmit(commandCount, commands))) {
             return;
         }

src/dawn_platform/tracing/EventTracer.cpp

@@ -0,0 +1,58 @@
+// Copyright 2019 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "dawn_platform/tracing/EventTracer.h"
+#include "common/Assert.h"
+#include "dawn_platform/DawnPlatform.h"
+
+namespace dawn_platform { namespace tracing {
+
+    const unsigned char* GetTraceCategoryEnabledFlag(Platform* platform, const char* name) {
+        static unsigned char disabled = 0;
+        if (platform == nullptr) {
+            return &disabled;
+        }
+
+        const unsigned char* categoryEnabledFlag = platform->GetTraceCategoryEnabledFlag(name);
+        if (categoryEnabledFlag != nullptr) {
+            return categoryEnabledFlag;
+        }
+
+        return &disabled;
+    }
+
+    TraceEventHandle AddTraceEvent(Platform* platform,
+                                   char phase,
+                                   const unsigned char* categoryGroupEnabled,
+                                   const char* name,
+                                   uint64_t id,
+                                   int numArgs,
+                                   const char** argNames,
+                                   const unsigned char* argTypes,
+                                   const uint64_t* argValues,
+                                   unsigned char flags) {
+        ASSERT(platform != nullptr);
+
+        double timestamp = platform->MonotonicallyIncreasingTime();
+        if (timestamp != 0) {
+            TraceEventHandle handle =
+                platform->AddTraceEvent(phase, categoryGroupEnabled, name, id, timestamp, numArgs,
+                                        argNames, argTypes, argValues, flags);
+            return handle;
+        }
+
+        return static_cast<TraceEventHandle>(0);
+    }
+
+}}  // namespace dawn_platform::tracing

src/dawn_platform/tracing/EventTracer.h

@@ -0,0 +1,43 @@
+// Copyright 2019 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef DAWNPLATFORM_TRACING_EVENTTRACER_H_
+#define DAWNPLATFORM_TRACING_EVENTTRACER_H_
+
+#include <stdint.h>
+
+namespace dawn_platform {
+
+    class Platform;
+
+    namespace tracing {
+
+        using TraceEventHandle = uint64_t;
+
+        const unsigned char* GetTraceCategoryEnabledFlag(Platform* platform, const char* name);
+        TraceEventHandle AddTraceEvent(Platform* platform,
+                                       char phase,
+                                       const unsigned char* categoryGroupEnabled,
+                                       const char* name,
+                                       uint64_t id,
+                                       int numArgs,
+                                       const char** argNames,
+                                       const unsigned char* argTypes,
+                                       const uint64_t* argValues,
+                                       unsigned char flags);
+
+    }  // namespace tracing
+}  // namespace dawn_platform
+
+#endif  // DAWNPLATFORM_TRACING_EVENTTRACER_H_

src/dawn_platform/tracing/TraceEvent.h

@@ -0,0 +1,990 @@
+// Copyright 2019 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Trace events are for tracking application performance and resource usage.
+// Macros are provided to track:
+//    Begin and end of function calls
+//    Counters
+//
+// Events are issued against categories. Whereas LOG's
+// categories are statically defined, TRACE categories are created
+// implicitly with a string. For example:
+//   TRACE_EVENT_INSTANT0("MY_SUBSYSTEM", "SomeImportantEvent")
+//
+// Events can be INSTANT, or can be pairs of BEGIN and END in the same scope:
+//   TRACE_EVENT_BEGIN0("MY_SUBSYSTEM", "SomethingCostly")
+//   doSomethingCostly()
+//   TRACE_EVENT_END0("MY_SUBSYSTEM", "SomethingCostly")
+// Note: our tools can't always determine the correct BEGIN/END pairs unless
+// these are used in the same scope. Use ASYNC_BEGIN/ASYNC_END macros if you need them
+// to be in separate scopes.
+//
+// A common use case is to trace entire function scopes. This
+// issues a trace BEGIN and END automatically:
+//   void doSomethingCostly() {
+//     TRACE_EVENT0("MY_SUBSYSTEM", "doSomethingCostly");
+//     ...
+//   }
+//
+// Additional parameters can be associated with an event:
+//   void doSomethingCostly2(int howMuch) {
+//     TRACE_EVENT1("MY_SUBSYSTEM", "doSomethingCostly",
+//         "howMuch", howMuch);
+//     ...
+//   }
+//
+// The trace system will automatically add to this information the
+// current process id, thread id, and a timestamp in microseconds.
+//
+// To trace an asynchronous procedure such as an IPC send/receive, use ASYNC_BEGIN and
+// ASYNC_END:
+//   [single threaded sender code]
+//     static int send_count = 0;
+//     ++send_count;
+//     TRACE_EVENT_ASYNC_BEGIN0("ipc", "message", send_count);
+//     Send(new MyMessage(send_count));
+//   [receive code]
+//     void OnMyMessage(send_count) {
+//       TRACE_EVENT_ASYNC_END0("ipc", "message", send_count);
+//     }
+// The third parameter is a unique ID to match ASYNC_BEGIN/ASYNC_END pairs.
+// ASYNC_BEGIN and ASYNC_END can occur on any thread of any traced process. Pointers can
+// be used for the ID parameter, and they will be mangled internally so that
+// the same pointer on two different processes will not match. For example:
+//   class MyTracedClass {
+//    public:
+//     MyTracedClass() {
+//       TRACE_EVENT_ASYNC_BEGIN0("category", "MyTracedClass", this);
+//     }
+//     ~MyTracedClass() {
+//       TRACE_EVENT_ASYNC_END0("category", "MyTracedClass", this);
+//     }
+//   }
+//
+// Trace event also supports counters, which is a way to track a quantity
+// as it varies over time. Counters are created with the following macro:
+//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter", g_myCounterValue);
+//
+// Counters are process-specific. The macro itself can be issued from any
+// thread, however.
+//
+// Sometimes, you want to track two counters at once. You can do this with two
+// counter macros:
+//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter0", g_myCounterValue[0]);
+//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter1", g_myCounterValue[1]);
+// Or you can do it with a combined macro:
+//   TRACE_COUNTER2("MY_SUBSYSTEM", "myCounter",
+//       "bytesPinned", g_myCounterValue[0],
+//       "bytesAllocated", g_myCounterValue[1]);
+// This indicates to the tracing UI that these counters should be displayed
+// in a single graph, as a summed area chart.
+//
+// Since counters are in a global namespace, you may want to disembiguate with a
+// unique ID, by using the TRACE_COUNTER_ID* variations.
+//
+// By default, trace collection is compiled in, but turned off at runtime.
+// Collecting trace data is the responsibility of the embedding
+// application. In Chrome's case, navigating to about:tracing will turn on
+// tracing and display data collected across all active processes.
+//
+//
+// Memory scoping note:
+// Tracing copies the pointers, not the string content, of the strings passed
+// in for category, name, and arg_names. Thus, the following code will
+// cause problems:
+//     char* str = strdup("impprtantName");
+//     TRACE_EVENT_INSTANT0("SUBSYSTEM", str);  // BAD!
+//     free(str);                   // Trace system now has dangling pointer
+//
+// To avoid this issue with the |name| and |arg_name| parameters, use the
+// TRACE_EVENT_COPY_XXX overloads of the macros at additional runtime overhead.
+// Notes: The category must always be in a long-lived char* (i.e. static const).
+//        The |arg_values|, when used, are always deep copied with the _COPY
+//        macros.
+//
+// When are string argument values copied:
+// const char* arg_values are only referenced by default:
+//     TRACE_EVENT1("category", "name",
+//                  "arg1", "literal string is only referenced");
+// Use TRACE_STR_COPY to force copying of a const char*:
+//     TRACE_EVENT1("category", "name",
+//                  "arg1", TRACE_STR_COPY("string will be copied"));
+// std::string arg_values are always copied:
+//     TRACE_EVENT1("category", "name",
+//                  "arg1", std::string("string will be copied"));
+//
+//
+// Thread Safety:
+// A thread safe singleton and mutex are used for thread safety. Category
+// enabled flags are used to limit the performance impact when the system
+// is not enabled.
+//
+// TRACE_EVENT macros first cache a pointer to a category. The categories are
+// statically allocated and safe at all times, even after exit. Fetching a
+// category is protected by the TraceLog::lock_. Multiple threads initializing
+// the static variable is safe, as they will be serialized by the lock and
+// multiple calls will return the same pointer to the category.
+//
+// Then the category_enabled flag is checked. This is a unsigned char, and
+// not intended to be multithread safe. It optimizes access to addTraceEvent
+// which is threadsafe internally via TraceLog::lock_. The enabled flag may
+// cause some threads to incorrectly call or skip calling addTraceEvent near
+// the time of the system being enabled or disabled. This is acceptable as
+// we tolerate some data loss while the system is being enabled/disabled and
+// because addTraceEvent is threadsafe internally and checks the enabled state
+// again under lock.
+//
+// Without the use of these static category pointers and enabled flags all
+// trace points would carry a significant performance cost of aquiring a lock
+// and resolving the category.
+
+#ifndef DAWNPLATFORM_TRACING_TRACEEVENT_H_
+#define DAWNPLATFORM_TRACING_TRACEEVENT_H_
+
+#include <string>
+
+#include "dawn_platform/tracing/EventTracer.h"
+
+#define TRACE_DISABLED_BY_DEFAULT(name) "disabled-by-default-" name
+
+// By default, const char* argument values are assumed to have long-lived scope
+// and will not be copied. Use this macro to force a const char* to be copied.
+#define TRACE_STR_COPY(str) WebCore::TraceEvent::TraceStringWithCopy(str)
+
+// Records a pair of begin and end events called "name" for the current
+// scope, with 0, 1 or 2 associated arguments. If the category is not
+// enabled, then this does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_EVENT0(platform, category, name) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(platform, category, name)
+#define TRACE_EVENT1(platform, category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(platform, category, name, arg1_name, arg1_val)
+#define TRACE_EVENT2(platform, category, name, arg1_name, arg1_val, arg2_name, arg2_val)      \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(platform, category, name, arg1_name, arg1_val, arg2_name, \
+                                    arg2_val)
+
+// Records a single event called "name" immediately, with 0, 1 or 2
+// associated arguments. If the category is not enabled, then this
+// does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_EVENT_INSTANT0(platform, category, name)                            \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name, \
+                             TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_INSTANT1(platform, category, name, arg1_name, arg1_val)       \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name, \
+                             TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_INSTANT2(platform, category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name,                \
+                             TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_INSTANT0(platform, category, name)                       \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name, \
+                             TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_INSTANT1(platform, category, name, arg1_name, arg1_val)  \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name, \
+                             TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_INSTANT2(platform, category, name, arg1_name, arg1_val, arg2_name, \
+                                  arg2_val)                                                 \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_INSTANT, category, name,           \
+                             TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name, arg2_val)
+
+// Records a single BEGIN event called "name" immediately, with 0, 1 or 2
+// associated arguments. If the category is not enabled, then this
+// does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_EVENT_BEGIN0(platform, category, name)                            \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name, \
+                             TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_BEGIN1(platform, category, name, arg1_name, arg1_val)       \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name, \
+                             TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_BEGIN2(platform, category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name,                \
+                             TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_BEGIN0(platform, category, name)                       \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name, \
+                             TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_BEGIN1(platform, category, name, arg1_name, arg1_val)  \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name, \
+                             TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_BEGIN2(platform, category, name, arg1_name, arg1_val, arg2_name, \
+                                arg2_val)                                                 \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_BEGIN, category, name,           \
+                             TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name, arg2_val)
+
+// Records a single END event for "name" immediately. If the category
+// is not enabled, then this does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_EVENT_END0(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_END1(category, name, arg1_name, arg1_val)                              \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_NONE, \
+                             arg1_name, arg1_val)
+#define TRACE_EVENT_END2(category, name, arg1_name, arg1_val, arg2_name, arg2_val)         \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_NONE, \
+                             arg1_name, arg1_val, arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_END0(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_END1(category, name, arg1_name, arg1_val)                         \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_COPY, \
+                             arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_END2(category, name, arg1_name, arg1_val, arg2_name, arg2_val)    \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, category, name, TRACE_EVENT_FLAG_COPY, \
+                             arg1_name, arg1_val, arg2_name, arg2_val)
+
+// Records the value of a counter called "name" immediately. Value
+// must be representable as a 32 bit integer.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_COUNTER1(platform, category, name, value)                           \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_COUNTER, category, name, \
+                             TRACE_EVENT_FLAG_NONE, "value", static_cast<int>(value))
+#define TRACE_COPY_COUNTER1(platform, category, name, value)                      \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_COUNTER, category, name, \
+                             TRACE_EVENT_FLAG_COPY, "value", static_cast<int>(value))
+
+// Records the values of a multi-parted counter called "name" immediately.
+// The UI will treat value1 and value2 as parts of a whole, displaying their
+// values as a stacked-bar chart.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_COUNTER2(platform, category, name, value1_name, value1_val, value2_name, value2_val) \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_COUNTER, category, name,                  \
+                             TRACE_EVENT_FLAG_NONE, value1_name, static_cast<int>(value1_val),     \
+                             value2_name, static_cast<int>(value2_val))
+#define TRACE_COPY_COUNTER2(platform, category, name, value1_name, value1_val, value2_name,    \
+                            value2_val)                                                        \
+    INTERNAL_TRACE_EVENT_ADD(platform, TRACE_EVENT_PHASE_COUNTER, category, name,              \
+                             TRACE_EVENT_FLAG_COPY, value1_name, static_cast<int>(value1_val), \
+                             value2_name, static_cast<int>(value2_val))
+
+// Records the value of a counter called "name" immediately. Value
+// must be representable as a 32 bit integer.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+// - |id| is used to disambiguate counters with the same name. It must either
+//   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
+//   will be xored with a hash of the process ID so that the same pointer on
+//   two different processes will not collide.
+#define TRACE_COUNTER_ID1(platform, category, name, id, value)                                \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_COUNTER, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, "value", static_cast<int>(value))
+#define TRACE_COPY_COUNTER_ID1(platform, category, name, id, value)                           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_COUNTER, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, "value", static_cast<int>(value))
+
+// Records the values of a multi-parted counter called "name" immediately.
+// The UI will treat value1 and value2 as parts of a whole, displaying their
+// values as a stacked-bar chart.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+// - |id| is used to disambiguate counters with the same name. It must either
+//   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
+//   will be xored with a hash of the process ID so that the same pointer on
+//   two different processes will not collide.
+#define TRACE_COUNTER_ID2(platform, category, name, id, value1_name, value1_val, value2_name, \
+                          value2_val)                                                         \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(                                                         \
+        platform, TRACE_EVENT_PHASE_COUNTER, category, name, id, TRACE_EVENT_FLAG_NONE,       \
+        value1_name, static_cast<int>(value1_val), value2_name, static_cast<int>(value2_val))
+#define TRACE_COPY_COUNTER_ID2(platform, category, name, id, value1_name, value1_val, value2_name, \
+                               value2_val)                                                         \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(                                                              \
+        platform, TRACE_EVENT_PHASE_COUNTER, category, name, id, TRACE_EVENT_FLAG_COPY,            \
+        value1_name, static_cast<int>(value1_val), value2_name, static_cast<int>(value2_val))
+
+// Records a single ASYNC_BEGIN event called "name" immediately, with 0, 1 or 2
+// associated arguments. If the category is not enabled, then this
+// does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+// - |id| is used to match the ASYNC_BEGIN event with the ASYNC_END event. ASYNC
+//   events are considered to match if their category, name and id values all
+//   match. |id| must either be a pointer or an integer value up to 64 bits. If
+//   it's a pointer, the bits will be xored with a hash of the process ID so
+//   that the same pointer on two different processes will not collide.
+// An asynchronous operation can consist of multiple phases. The first phase is
+// defined by the ASYNC_BEGIN calls. Additional phases can be defined using the
+// ASYNC_STEP_BEGIN macros. When the operation completes, call ASYNC_END.
+// An async operation can span threads and processes, but all events in that
+// operation must use the same |name| and |id|. Each event can have its own
+// args.
+#define TRACE_EVENT_ASYNC_BEGIN0(platform, category, name, id)                                    \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_ASYNC_BEGIN1(platform, category, name, id, arg1_name, arg1_val)               \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_ASYNC_BEGIN2(platform, category, name, id, arg1_name, arg1_val, arg2_name,    \
+                                 arg2_val)                                                        \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name,       \
+                                     arg2_val)
+#define TRACE_EVENT_COPY_ASYNC_BEGIN0(platform, category, name, id)                               \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_ASYNC_BEGIN1(platform, category, name, id, arg1_name, arg1_val)          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_BEGIN2(platform, category, name, id, arg1_name, arg1_val,          \
+                                      arg2_name, arg2_val)                                        \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_BEGIN, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name,       \
+                                     arg2_val)
+
+// Records a single ASYNC_STEP event for |step| immediately. If the category
+// is not enabled, then this does nothing. The |name| and |id| must match the
+// ASYNC_BEGIN event above. The |step| param identifies this step within the
+// async event. This should be called at the beginning of the next phase of an
+// asynchronous operation.
+#define TRACE_EVENT_ASYNC_STEP0(platform, category, name, id, step)                              \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_STEP, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, "step", step)
+#define TRACE_EVENT_ASYNC_STEP1(platform, category, name, id, step, arg1_name, arg1_val)         \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_STEP, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, "step", step, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_STEP0(platform, category, name, id, step)                         \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_STEP, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, "step", step)
+#define TRACE_EVENT_COPY_ASYNC_STEP1(platform, category, name, id, step, arg1_name, arg1_val)    \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_STEP, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, "step", step, arg1_name, arg1_val)
+
+// Records a single ASYNC_END event for "name" immediately. If the category
+// is not enabled, then this does nothing.
+#define TRACE_EVENT_ASYNC_END0(platform, category, name, id)                                    \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_ASYNC_END1(platform, category, name, id, arg1_name, arg1_val)               \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_ASYNC_END2(platform, category, name, id, arg1_name, arg1_val, arg2_name,    \
+                               arg2_val)                                                        \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id, \
+                                     TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name,     \
+                                     arg2_val)
+#define TRACE_EVENT_COPY_ASYNC_END0(platform, category, name, id)                               \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_ASYNC_END1(platform, category, name, id, arg1_name, arg1_val)          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id, \
+                                     TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_END2(platform, category, name, id, arg1_name, arg1_val, arg2_name, \
+                                    arg2_val)                                                     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_ASYNC_END, category, name, id,   \
+                                     TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name,       \
+                                     arg2_val)
+
+// NESTABLE_ASYNC_* APIs are used to describe an async operation, which can
+// be nested within a NESTABLE_ASYNC event and/or have inner NESTABLE_ASYNC
+// events.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+// - A pair of NESTABLE_ASYNC_BEGIN event and NESTABLE_ASYNC_END event is
+//   considered as a match if their category_group, name and id all match.
+// - |id| must either be a pointer or an integer value up to 64 bits.
+//   If it's a pointer, the bits will be xored with a hash of the process ID so
+//   that the same pointer on two different processes will not collide.
+// - |id| is used to match a child NESTABLE_ASYNC event with its parent
+//   NESTABLE_ASYNC event. Therefore, events in the same nested event tree must
+//   be logged using the same id and category_group.
+//
+// Unmatched NESTABLE_ASYNC_END event will be parsed as an event that starts
+// at the first NESTABLE_ASYNC event of that id, and unmatched
+// NESTABLE_ASYNC_BEGIN event will be parsed as an event that ends at the last
+// NESTABLE_ASYNC event of that id. Corresponding warning messages for
+// unmatched events will be shown in the analysis view.
+
+// Records a single NESTABLE_ASYNC_BEGIN event called "name" immediately, with
+// 0, 1 or 2 associated arguments. If the category is not enabled, then this
+// does nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(platform, category_group, name, id)          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN, \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_NESTABLE_ASYNC_BEGIN1(platform, category_group, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN,             \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name,   \
+                                     arg1_val)
+#define TRACE_EVENT_NESTABLE_ASYNC_BEGIN2(platform, category_group, name, id, arg1_name, arg1_val, \
+                                          arg2_name, arg2_val)                                     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN,             \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name,   \
+                                     arg1_val, arg2_name, arg2_val)
+// Records a single NESTABLE_ASYNC_END event called "name" immediately, with 0
+// or 2 associated arguments. If the category is not enabled, then this does
+// nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_END0(platform, category_group, name, id)          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE)
+// Records a single NESTABLE_ASYNC_END event called "name" immediately, with 1
+// associated argument. If the category is not enabled, then this does nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_END1(platform, category_group, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END,             \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, \
+                                     arg1_val)
+#define TRACE_EVENT_NESTABLE_ASYNC_END2(platform, category_group, name, id, arg1_name, arg1_val, \
+                                        arg2_name, arg2_val)                                     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END,             \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, \
+                                     arg1_val, arg2_name, arg2_val)
+
+// Records a single NESTABLE_ASYNC_INSTANT event called "name" immediately,
+// with none, one or two associated argument. If the category is not enabled,
+// then this does nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_INSTANT0(platform, category_group, name, id)          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT, \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE)
+
+#define TRACE_EVENT_NESTABLE_ASYNC_INSTANT1(platform, category_group, name, id, arg1_name,       \
+                                            arg1_val)                                            \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT,         \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, \
+                                     arg1_val)
+
+#define TRACE_EVENT_NESTABLE_ASYNC_INSTANT2(platform, category_group, name, id, arg1_name,       \
+                                            arg1_val, arg2_name, arg2_val)                       \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT,         \
+                                     category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, \
+                                     arg1_val, arg2_name, arg2_val)
+
+#define TRACE_EVENT_COPY_NESTABLE_ASYNC_BEGIN_WITH_TTS2(platform, category_group, name, id,       \
+                                                        arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN,            \
+                                     category_group, name, id,                                    \
+                                     TRACE_EVENT_FLAG_ASYNC_TTS | TRACE_EVENT_FLAG_COPY,          \
+                                     arg1_name, arg1_val, arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_NESTABLE_ASYNC_END_WITH_TTS2(platform, category_group, name, id,       \
+                                                      arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END,            \
+                                     category_group, name, id,                                  \
+                                     TRACE_EVENT_FLAG_ASYNC_TTS | TRACE_EVENT_FLAG_COPY,        \
+                                     arg1_name, arg1_val, arg2_name, arg2_val)
+
+// Similar to TRACE_EVENT_NESTABLE_ASYNC_{BEGIN,END}x but with a custom
+// |timestamp| provided.
+#define TRACE_EVENT_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(platform, category_group, name, id, \
+                                                         timestamp)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                      \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN, category_group, name, id,          \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(platform, category_group, name, id, \
+                                                       timestamp)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                    \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, category_group, name, id,          \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_NESTABLE_ASYNC_END_WITH_TIMESTAMP1(platform, category_group, name, id, \
+                                                       timestamp, arg1_name, arg1_val)     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                    \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, category_group, name, id,          \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_NESTABLE_ASYNC_INSTANT_WITH_TIMESTAMP0(platform, category_group, name, id, \
+                                                           timestamp)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                        \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT, category_group, name, id,          \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_COPY_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(platform, category_group, name, id, \
+                                                              timestamp)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                           \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN, category_group, name, id,               \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(platform, category_group, name, id, \
+                                                            timestamp)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                                         \
+        platform, TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, category_group, name, id,               \
+        TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, TRACE_EVENT_FLAG_COPY)
+
+// Records a single FLOW_BEGIN event called "name" immediately, with 0, 1 or 2
+// associated arguments. If the category is not enabled, then this
+// does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+// - |id| is used to match the FLOW_BEGIN event with the FLOW_END event. FLOW
+//   events are considered to match if their category_group, name and id values
+//   all match. |id| must either be a pointer or an integer value up to 64 bits.
+//   If it's a pointer, the bits will be xored with a hash of the process ID so
+//   that the same pointer on two different processes will not collide.
+// FLOW events are different from ASYNC events in how they are drawn by the
+// tracing UI. A FLOW defines asynchronous data flow, such as posting a task
+// (FLOW_BEGIN) and later executing that task (FLOW_END). Expect FLOWs to be
+// drawn as lines or arrows from FLOW_BEGIN scopes to FLOW_END scopes. Similar
+// to ASYNC, a FLOW can consist of multiple phases. The first phase is defined
+// by the FLOW_BEGIN calls. Additional phases can be defined using the FLOW_STEP
+// macros. When the operation completes, call FLOW_END. An async operation can
+// span threads and processes, but all events in that operation must use the
+// same |name| and |id|. Each event can have its own args.
+#define TRACE_EVENT_FLOW_BEGIN0(platform, category_group, name, id)                                \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_FLOW_BEGIN1(platform, category_group, name, id, arg1_name, arg1_val)           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_FLOW_BEGIN2(platform, category_group, name, id, arg1_name, arg1_val,           \
+                                arg2_name, arg2_val)                                               \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name,    \
+                                     arg2_val)
+#define TRACE_EVENT_COPY_FLOW_BEGIN0(platform, category_group, name, id)                           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_FLOW_BEGIN1(platform, category_group, name, id, arg1_name, arg1_val)      \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_FLOW_BEGIN2(platform, category_group, name, id, arg1_name, arg1_val,      \
+                                     arg2_name, arg2_val)                                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_BEGIN, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name,    \
+                                     arg2_val)
+
+// Records a single FLOW_STEP event for |step| immediately. If the category
+// is not enabled, then this does nothing. The |name| and |id| must match the
+// FLOW_BEGIN event above. The |step| param identifies this step within the
+// async event. This should be called at the beginning of the next phase of an
+// asynchronous operation.
+#define TRACE_EVENT_FLOW_STEP0(platform, category_group, name, id, step)                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_STEP, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE, "step", step)
+#define TRACE_EVENT_FLOW_STEP1(platform, category_group, name, id, step, arg1_name, arg1_val)     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_STEP, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE, "step", step, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_FLOW_STEP0(platform, category_group, name, id, step)                     \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_STEP, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY, "step", step)
+#define TRACE_EVENT_COPY_FLOW_STEP1(platform, category_group, name, id, step, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_STEP, category_group, name,  \
+                                     id, TRACE_EVENT_FLAG_COPY, "step", step, arg1_name, arg1_val)
+
+// Records a single FLOW_END event for "name" immediately. If the category
+// is not enabled, then this does nothing.
+#define TRACE_EVENT_FLOW_END0(platform, category_group, name, id)                                \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_FLOW_END_BIND_TO_ENCLOSING0(platform, category_group, name, id)              \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_BIND_TO_ENCLOSING)
+#define TRACE_EVENT_FLOW_END1(platform, category_group, name, id, arg1_name, arg1_val)           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_FLOW_END2(platform, category_group, name, id, arg1_name, arg1_val, arg2_name, \
+                              arg2_val)                                                           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name,  \
+                                     id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name,   \
+                                     arg2_val)
+#define TRACE_EVENT_COPY_FLOW_END0(platform, category_group, name, id)                           \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_FLOW_END1(platform, category_group, name, id, arg1_name, arg1_val)      \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_FLOW_END2(platform, category_group, name, id, arg1_name, arg1_val,      \
+                                   arg2_name, arg2_val)                                          \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, TRACE_EVENT_PHASE_FLOW_END, category_group, name, \
+                                     id, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, arg2_name,  \
+                                     arg2_val)
+
+// Creates a scope of a sampling state with the given category and name (both must
+// be constant strings). These states are intended for a sampling profiler.
+// Implementation note: we store category and name together because we don't
+// want the inconsistency/expense of storing two pointers.
+// |thread_bucket| is [0..2] and is used to statically isolate samples in one
+// thread from others.
+//
+// {  // The sampling state is set within this scope.
+//    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
+//    ...;
+// }
+#define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, name) \
+    TraceEvent::SamplingStateScope<bucket_number> traceEventSamplingScope(category "\0" name);
+
+// Returns a current sampling state of the given bucket.
+// The format of the returned string is "category\0name".
+#define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
+    TraceEvent::SamplingStateScope<bucket_number>::current()
+
+// Sets a current sampling state of the given bucket.
+// |category| and |name| have to be constant strings.
+#define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, name) \
+    TraceEvent::SamplingStateScope<bucket_number>::set(category "\0" name)
+
+// Sets a current sampling state of the given bucket.
+// |categoryAndName| doesn't need to be a constant string.
+// The format of the string is "category\0name".
+#define TRACE_EVENT_SET_NONCONST_SAMPLING_STATE_FOR_BUCKET(bucket_number, categoryAndName) \
+    TraceEvent::SamplingStateScope<bucket_number>::set(categoryAndName)
+
+// Syntactic sugars for the sampling tracing in the main thread.
+#define TRACE_EVENT_SCOPED_SAMPLING_STATE(category, name) \
+    TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(0, category, name)
+#define TRACE_EVENT_GET_SAMPLING_STATE() TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(0)
+#define TRACE_EVENT_SET_SAMPLING_STATE(category, name) \
+    TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(0, category, name)
+#define TRACE_EVENT_SET_NONCONST_SAMPLING_STATE(categoryAndName) \
+    TRACE_EVENT_SET_NONCONST_SAMPLING_STATE_FOR_BUCKET(0, categoryAndName)
+
+////////////////////////////////////////////////////////////////////////////////
+// Implementation specific tracing API definitions.
+
+// Get a pointer to the enabled state of the given trace category. Only
+// long-lived literal strings should be given as the category name. The returned
+// pointer can be held permanently in a local static for example. If the
+// unsigned char is non-zero, tracing is enabled. If tracing is enabled,
+// TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
+// between the load of the tracing state and the call to
+// TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
+// for best performance when tracing is disabled.
+// const unsigned char*
+//     TRACE_EVENT_API_GET_CATEGORY_ENABLED(const char* category_name)
+#define TRACE_EVENT_API_GET_CATEGORY_ENABLED dawn_platform::tracing::GetTraceCategoryEnabledFlag
+
+// Add a trace event to the platform tracing system.
+// void TRACE_EVENT_API_ADD_TRACE_EVENT(
+//                    char phase,
+//                    const unsigned char* category_enabled,
+//                    const char* name,
+//                    unsigned long long id,
+//                    int num_args,
+//                    const char** arg_names,
+//                    const unsigned char* arg_types,
+//                    const unsigned long long* arg_values,
+//                    unsigned char flags)
+#define TRACE_EVENT_API_ADD_TRACE_EVENT dawn_platform::tracing::AddTraceEvent
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Implementation detail: trace event macros create temporary variables
+// to keep instrumentation overhead low. These macros give each temporary
+// variable a unique name based on the line number to prevent name collissions.
+#define INTERNAL_TRACE_EVENT_UID3(a, b) trace_event_unique_##a##b
+#define INTERNAL_TRACE_EVENT_UID2(a, b) INTERNAL_TRACE_EVENT_UID3(a, b)
+#define INTERNALTRACEEVENTUID(name_prefix) INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
+
+// Implementation detail: internal macro to create static category.
+#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(platform, category)    \
+    static const unsigned char* INTERNALTRACEEVENTUID(catstatic) = 0; \
+    if (!INTERNALTRACEEVENTUID(catstatic))                            \
+        INTERNALTRACEEVENTUID(catstatic) = TRACE_EVENT_API_GET_CATEGORY_ENABLED(platform, category);
+
+// Implementation detail: internal macro to create static category and add
+// event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_ADD(platform, phase, category, name, flags, ...) \
+    do {                                                                      \
+        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(platform, category);           \
+        if (*INTERNALTRACEEVENTUID(catstatic)) {                              \
+            dawn_platform::TraceEvent::addTraceEvent(                         \
+                platform, phase, INTERNALTRACEEVENTUID(catstatic), name,      \
+                dawn_platform::TraceEvent::noEventId, flags, ##__VA_ARGS__);  \
+        }                                                                     \
+    } while (0)
+
+// Implementation detail: internal macro to create static category and add begin
+// event if the category is enabled. Also adds the end event when the scope
+// ends.
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED(platform, category, name, ...)                   \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(platform, category);                          \
+    dawn_platform::TraceEvent::TraceEndOnScopeClose INTERNALTRACEEVENTUID(profileScope); \
+    if (*INTERNALTRACEEVENTUID(catstatic)) {                                             \
+        dawn_platform::TraceEvent::addTraceEvent(                                        \
+            platform, TRACE_EVENT_PHASE_BEGIN, INTERNALTRACEEVENTUID(catstatic), name,   \
+            dawn_platform::TraceEvent::noEventId, TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
+        INTERNALTRACEEVENTUID(profileScope)                                              \
+            .initialize(platform, INTERNALTRACEEVENTUID(catstatic), name);               \
+    }
+
+// Implementation detail: internal macro to create static category and add
+// event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(platform, phase, category, name, id, flags, ...)          \
+    do {                                                                                           \
+        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(platform, category);                                \
+        if (*INTERNALTRACEEVENTUID(catstatic)) {                                                   \
+            unsigned char traceEventFlags = flags | TRACE_EVENT_FLAG_HAS_ID;                       \
+            dawn_platform::TraceEvent::TraceID traceEventTraceID(id, &traceEventFlags);            \
+            dawn_platform::TraceEvent::addTraceEvent(                                              \
+                platform, phase, INTERNALTRACEEVENTUID(catstatic), name, traceEventTraceID.data(), \
+                traceEventFlags, ##__VA_ARGS__);                                                   \
+        }                                                                                          \
+    } while (0)
+
+// Notes regarding the following definitions:
+// New values can be added and propagated to third party libraries, but existing
+// definitions must never be changed, because third party libraries may use old
+// definitions.
+
+// Phase indicates the nature of an event entry. E.g. part of a begin/end pair.
+#define TRACE_EVENT_PHASE_BEGIN ('B')
+#define TRACE_EVENT_PHASE_END ('E')
+#define TRACE_EVENT_PHASE_INSTANT ('I')
+#define TRACE_EVENT_PHASE_ASYNC_BEGIN ('S')
+#define TRACE_EVENT_PHASE_ASYNC_STEP ('T')
+#define TRACE_EVENT_PHASE_ASYNC_END ('F')
+#define TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN ('b')
+#define TRACE_EVENT_PHASE_NESTABLE_ASYNC_END ('e')
+#define TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT ('n')
+#define TRACE_EVENT_PHASE_FLOW_BEGIN ('s')
+#define TRACE_EVENT_PHASE_FLOW_STEP ('t')
+#define TRACE_EVENT_PHASE_FLOW_END ('f')
+#define TRACE_EVENT_PHASE_METADATA ('M')
+#define TRACE_EVENT_PHASE_COUNTER ('C')
+#define TRACE_EVENT_PHASE_SAMPLE ('P')
+
+// Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
+#define TRACE_EVENT_FLAG_NONE (static_cast<unsigned char>(0))
+#define TRACE_EVENT_FLAG_COPY (static_cast<unsigned char>(1 << 0))
+#define TRACE_EVENT_FLAG_HAS_ID (static_cast<unsigned char>(1 << 1))
+#define TRACE_EVENT_FLAG_MANGLE_ID (static_cast<unsigned char>(1 << 2))
+
+// Type values for identifying types in the TraceValue union.
+#define TRACE_VALUE_TYPE_BOOL (static_cast<unsigned char>(1))
+#define TRACE_VALUE_TYPE_UINT (static_cast<unsigned char>(2))
+#define TRACE_VALUE_TYPE_INT (static_cast<unsigned char>(3))
+#define TRACE_VALUE_TYPE_DOUBLE (static_cast<unsigned char>(4))
+#define TRACE_VALUE_TYPE_POINTER (static_cast<unsigned char>(5))
+#define TRACE_VALUE_TYPE_STRING (static_cast<unsigned char>(6))
+#define TRACE_VALUE_TYPE_COPY_STRING (static_cast<unsigned char>(7))
+
+namespace dawn_platform { namespace TraceEvent {
+
+    // Specify these values when the corresponding argument of addTraceEvent is not
+    // used.
+    const int zeroNumArgs = 0;
+    const unsigned long long noEventId = 0;
+
+    // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
+    // are mangled with the Process ID so that they are unlikely to collide when the
+    // same pointer is used on different processes.
+    class TraceID {
+      public:
+        explicit TraceID(const void* id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(reinterpret_cast<uintptr_t>(id))) {
+            *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
+        }
+        explicit TraceID(unsigned long long id, unsigned char* flags) : m_data(id) {
+            (void)flags;
+        }
+        explicit TraceID(unsigned long id, unsigned char* flags) : m_data(id) {
+            (void)flags;
+        }
+        explicit TraceID(unsigned int id, unsigned char* flags) : m_data(id) {
+            (void)flags;
+        }
+        explicit TraceID(unsigned short id, unsigned char* flags) : m_data(id) {
+            (void)flags;
+        }
+        explicit TraceID(unsigned char id, unsigned char* flags) : m_data(id) {
+            (void)flags;
+        }
+        explicit TraceID(long long id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(id)) {
+            (void)flags;
+        }
+        explicit TraceID(long id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(id)) {
+            (void)flags;
+        }
+        explicit TraceID(int id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(id)) {
+            (void)flags;
+        }
+        explicit TraceID(short id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(id)) {
+            (void)flags;
+        }
+        explicit TraceID(signed char id, unsigned char* flags)
+            : m_data(static_cast<unsigned long long>(id)) {
+            (void)flags;
+        }
+
+        unsigned long long data() const {
+            return m_data;
+        }
+
+      private:
+        unsigned long long m_data;
+    };
+
+    // Simple union to store various types as unsigned long long.
+    union TraceValueUnion {
+        bool m_bool;
+        unsigned long long m_uint;
+        long long m_int;
+        double m_double;
+        const void* m_pointer;
+        const char* m_string;
+    };
+
+    // Simple container for const char* that should be copied instead of retained.
+    class TraceStringWithCopy {
+      public:
+        explicit TraceStringWithCopy(const char* str) : m_str(str) {
+        }
+        operator const char*() const {
+            return m_str;
+        }
+
+      private:
+        const char* m_str;
+    };
+
+// Define setTraceValue for each allowed type. It stores the type and
+// value in the return arguments. This allows this API to avoid declaring any
+// structures so that it is portable to third_party libraries.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, union_member, value_type_id) \
+    static inline void setTraceValue(actual_type arg, unsigned char* type,         \
+                                     unsigned long long* value) {                  \
+        TraceValueUnion typeValue;                                                 \
+        typeValue.union_member = arg;                                              \
+        *type = value_type_id;                                                     \
+        *value = typeValue.m_uint;                                                 \
+    }
+// Simpler form for int types that can be safely casted.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, value_type_id)   \
+    static inline void setTraceValue(actual_type arg, unsigned char* type, \
+                                     unsigned long long* value) {          \
+        *type = value_type_id;                                             \
+        *value = static_cast<unsigned long long>(arg);                     \
+    }
+
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long long, TRACE_VALUE_TYPE_UINT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
+        INTERNAL_DECLARE_SET_TRACE_VALUE(bool, m_bool, TRACE_VALUE_TYPE_BOOL)
+        INTERNAL_DECLARE_SET_TRACE_VALUE(double, m_double, TRACE_VALUE_TYPE_DOUBLE)
+        INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, m_pointer, TRACE_VALUE_TYPE_POINTER)
+        INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, m_string, TRACE_VALUE_TYPE_STRING)
+        INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&,
+                                         m_string,
+                                         TRACE_VALUE_TYPE_COPY_STRING)
+
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
+
+        static inline void setTraceValue(const std::string& arg,
+                                         unsigned char* type,
+                                         unsigned long long* value) {
+            TraceValueUnion typeValue;
+            typeValue.m_string = arg.data();
+            *type = TRACE_VALUE_TYPE_COPY_STRING;
+            *value = typeValue.m_uint;
+        }
+
+        // These addTraceEvent template functions are defined here instead of in the
+        // macro, because the arg values could be temporary string objects. In order to
+        // store pointers to the internal c_str and pass through to the tracing API, the
+        // arg values must live throughout these procedures.
+
+        static inline dawn_platform::tracing::TraceEventHandle addTraceEvent(
+            dawn_platform::Platform* platform,
+            char phase,
+            const unsigned char* categoryEnabled,
+            const char* name,
+            unsigned long long id,
+            unsigned char flags) {
+            return TRACE_EVENT_API_ADD_TRACE_EVENT(platform, phase, categoryEnabled, name, id,
+                                                   zeroNumArgs, 0, 0, 0, flags);
+        }
+
+        template <class ARG1_TYPE>
+        static inline dawn_platform::tracing::TraceEventHandle addTraceEvent(
+            dawn_platform::Platform* platform,
+            char phase,
+            const unsigned char* categoryEnabled,
+            const char* name,
+            unsigned long long id,
+            unsigned char flags,
+            const char* arg1Name,
+            const ARG1_TYPE& arg1Val) {
+            const int numArgs = 1;
+            unsigned char argTypes[1];
+            uint64_t argValues[1];
+            setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
+            return TRACE_EVENT_API_ADD_TRACE_EVENT(platform, phase, categoryEnabled, name, id,
+                                                   numArgs, &arg1Name, argTypes, argValues, flags);
+        }
+
+        template <class ARG1_TYPE, class ARG2_TYPE>
+        static inline dawn_platform::tracing::TraceEventHandle addTraceEvent(
+            dawn_platform::Platform* platform,
+            char phase,
+            const unsigned char* categoryEnabled,
+            const char* name,
+            unsigned long long id,
+            unsigned char flags,
+            const char* arg1Name,
+            const ARG1_TYPE& arg1Val,
+            const char* arg2Name,
+            const ARG2_TYPE& arg2Val) {
+            const int numArgs = 2;
+            const char* argNames[2] = {arg1Name, arg2Name};
+            unsigned char argTypes[2];
+            uint64_t argValues[2];
+            setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
+            setTraceValue(arg2Val, &argTypes[1], &argValues[1]);
+            return TRACE_EVENT_API_ADD_TRACE_EVENT(platform, phase, categoryEnabled, name, id,
+                                                   numArgs, argNames, argTypes, argValues, flags);
+        }
+
+        // Used by TRACE_EVENTx macro. Do not use directly.
+        class TraceEndOnScopeClose {
+          public:
+            // Note: members of m_data intentionally left uninitialized. See initialize.
+            TraceEndOnScopeClose() : m_pdata(0) {
+            }
+            ~TraceEndOnScopeClose() {
+                if (m_pdata)
+                    addEventIfEnabled();
+            }
+
+            void initialize(dawn_platform::Platform* platform,
+                            const unsigned char* categoryEnabled,
+                            const char* name) {
+                m_data.platform = platform;
+                m_data.categoryEnabled = categoryEnabled;
+                m_data.name = name;
+                m_pdata = &m_data;
+            }
+
+          private:
+            // Add the end event if the category is still enabled.
+            void addEventIfEnabled() {
+                // Only called when m_pdata is non-null.
+                if (*m_pdata->categoryEnabled) {
+                    TRACE_EVENT_API_ADD_TRACE_EVENT(
+                        m_pdata->platform, TRACE_EVENT_PHASE_END, m_pdata->categoryEnabled,
+                        m_pdata->name, noEventId, zeroNumArgs, 0, 0, 0, TRACE_EVENT_FLAG_NONE);
+                }
+            }
+
+            // This Data struct workaround is to avoid initializing all the members
+            // in Data during construction of this object, since this object is always
+            // constructed, even when tracing is disabled. If the members of Data were
+            // members of this class instead, compiler warnings occur about potential
+            // uninitialized accesses.
+            struct Data {
+                dawn_platform::Platform* platform;
+                const unsigned char* categoryEnabled;
+                const char* name;
+            };
+            Data* m_pdata;
+            Data m_data;
+        };
+
+}}  // namespace dawn_platform::TraceEvent
+
+#endif  // DAWNPLATFORM_TRACING_TRACEEVENT_H_

src/include/dawn_native/DawnNative.h

@@ -21,6 +21,10 @@
 #include <string>
 #include <vector>
 
+namespace dawn_platform {
+    class Platform;
+}  // namespace dawn_platform
+
 namespace dawn_native {
 
     struct PCIInfo {
@@ -140,6 +144,9 @@ namespace dawn_native {
         void EnableBeginCaptureOnStartup(bool beginCaptureOnStartup);
         bool IsBeginCaptureOnStartupEnabled() const;
 
+        void SetPlatform(dawn_platform::Platform* platform);
+        dawn_platform::Platform* GetPlatform() const;
+
       private:
         InstanceBase* mImpl = nullptr;
     };

src/include/dawn_platform/DawnPlatform.h

@@ -0,0 +1,46 @@
+// Copyright 2019 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef DAWNPLATFORM_DAWNPLATFORM_H_
+#define DAWNPLATFORM_DAWNPLATFORM_H_
+
+#include <dawn_native/dawn_native_export.h>
+
+#include <stdint.h>
+
+namespace dawn_platform {
+
+    class DAWN_NATIVE_EXPORT Platform {
+      public:
+        virtual ~Platform() {
+        }
+        virtual const unsigned char* GetTraceCategoryEnabledFlag(const char* name) = 0;
+
+        virtual double MonotonicallyIncreasingTime() = 0;
+
+        virtual uint64_t AddTraceEvent(char phase,
+                                       const unsigned char* categoryGroupEnabled,
+                                       const char* name,
+                                       uint64_t id,
+                                       double timestamp,
+                                       int numArgs,
+                                       const char** argNames,
+                                       const unsigned char* argTypes,
+                                       const uint64_t* argValues,
+                                       unsigned char flags) = 0;
+    };
+
+}  // namespace dawn_platform
+
+#endif  // DAWNPLATFORM_DAWNPLATFORM_H_