perf_tests: Manually serialize JSON and remove dependency on jsoncpp

jsoncpp causes some flaky failures because of inconsistencies in nested
DEPS. We barely use it for JSON serialization so the simplest solution
is to just manually write the serialization for perf test tracing data.

Bug: dawn:208
Change-Id: Ie5e4b5436e2c9e32e6817d64c6e95c774cb8751f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/14720
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>

BUILD.gn

@@ -1020,7 +1020,6 @@ test("dawn_perf_tests") {
     ":dawn_utils",
     ":libdawn_native",
     ":libdawn_wire",
-    "${dawn_jsoncpp_dir}:jsoncpp",
     "${dawn_root}/src/common",
     "${dawn_root}/src/dawn:dawncpp",
     "${dawn_root}/src/dawn:libdawn_proc",

DEPS

@@ -73,17 +73,6 @@ deps = {
     'condition': 'dawn_standalone',
   },
 
-  # jsoncpp for perf tests trace events
-  'third_party/jsoncpp': {
-    'url': '{chromium_git}/chromium/src/third_party/jsoncpp@571788934b5ee8643d53e5d054534abbe6006168',
-    'condition': 'dawn_standalone',
-  },
-
-  'third_party/jsoncpp/source': {
-    'url' : '{chromium_git}/external/github.com/open-source-parsers/jsoncpp@645250b6690785be60ab6780ce4b58698d884d11',
-    'condition': 'dawn_standalone',
-  },
-
   # GLFW for tests and samples
   'third_party/glfw': {
     'url': '{chromium_git}/external/github.com/glfw/glfw@2de2589f910b1a85905f425be4d32f33cec092df',

build_overrides/dawn.gni

@@ -27,7 +27,6 @@ dawn_standalone = true
 dawn_jinja2_dir = "//third_party/jinja2"
 dawn_glfw_dir = "//third_party/glfw"
 dawn_googletest_dir = "//third_party/googletest"
-dawn_jsoncpp_dir = "//third_party/jsoncpp"
 dawn_shaderc_dir = "//third_party/shaderc"
 dawn_spirv_tools_dir = "//third_party/SPIRV-Tools"
 dawn_spirv_cross_dir = "//third_party/spirv-cross"

scripts/dawn_overrides_with_defaults.gni

@@ -41,10 +41,6 @@ if (!defined(dawn_googletest_dir)) {
   dawn_googletest_dir = "//third_party/googletest"
 }
 
-if (!defined(dawn_jsoncpp_dir)) {
-  dawn_jsoncpp_dir = "//third_party/jsoncpp"
-}
-
 if (!defined(dawn_shaderc_dir)) {
   dawn_shaderc_dir = "//third_party/shaderc"
 }

src/tests/perf_tests/DawnPerfTest.cpp

@@ -20,9 +20,6 @@
 #include "tests/perf_tests/DawnPerfTestPlatform.h"
 #include "utils/Timer.h"
 
-#include <json/value.h>
-#include <json/writer.h>
-
 #include <fstream>
 #include <limits>
 
@@ -36,45 +33,37 @@ namespace {
         std::ofstream outFile;
         outFile.open(traceFile, std::ios_base::app);
 
-        Json::StreamWriterBuilder builder;
-        std::unique_ptr<Json::StreamWriter> writer(builder.newStreamWriter());
-
         for (const DawnPerfTestPlatform::TraceEvent& traceEvent : traceEventBuffer) {
-            Json::Value value(Json::objectValue);
+            const char* category = nullptr;
-
-            const Json::LargestInt microseconds =
-                static_cast<Json::LargestInt>(traceEvent.timestamp * 1000.0 * 1000.0);
-
-            char phase[2] = {traceEvent.phase, '\0'};
-
-            value["name"] = traceEvent.name;
             switch (traceEvent.category) {
                 case dawn_platform::TraceCategory::General:
-                    value["cat"] = "general";
+                    category = "general";
                     break;
                 case dawn_platform::TraceCategory::Validation:
-                    value["cat"] = "validation";
+                    category = "validation";
                     break;
                 case dawn_platform::TraceCategory::Recording:
-                    value["cat"] = "recording";
+                    category = "recording";
                     break;
                 case dawn_platform::TraceCategory::GPUWork:
-                    value["cat"] = "gpu";
+                    category = "gpu";
                     break;
                 default:
                     UNREACHABLE();
             }
-            value["ph"] = &phase[0];
-            value["id"] = traceEvent.id;
-            value["tid"] = traceEvent.threadId;
-            value["ts"] = microseconds;
-            value["pid"] = "Dawn";
 
-            outFile << ", ";
+            uint64_t microseconds = static_cast<uint64_t>(traceEvent.timestamp * 1000.0 * 1000.0);
-            writer->write(value, &outFile);
+
-            outFile.flush();
+            outFile << ", { "
+                    << "\"name\": \"" << traceEvent.name << "\", "
+                    << "\"cat\": \"" << category << "\", "
+                    << "\"ph\": \"" << traceEvent.phase << "\", "
+                    << "\"id\": " << traceEvent.id << ", "
+                    << "\"tid\": " << traceEvent.threadId << ", "
+                    << "\"ts\": " << microseconds << ", "
+                    << "\"pid\": \"Dawn\""
+                    << " }";
         }
-
         outFile.close();
     }
 
@@ -115,7 +104,7 @@ DawnPerfTestEnvironment::DawnPerfTestEnvironment(int argc, char** argv)
         if (strcmp("-h", argv[i]) == 0 || strcmp("--help", argv[i]) == 0) {
             dawn::InfoLog()
                 << "Additional flags:"
-                << " [--calibration] [--override-steps=x] [--enable-tracing] [--trace-file=file]\n"
+                << " [--calibration] [--override-steps=x] [--trace-file=file]\n"
                 << "  --calibration: Only run calibration. Calibration allows the perf test"
                    " runner script to save some time.\n"
                 << " --override-steps: Set a fixed number of steps to run for each test\n"