Split backend/common in backend/ and common/

This directory used to contain both the state tracking code for the
backends, and the common utilities that could be used both by the
backends and the rest of the code. Things are now:

 - src/common is utility code for the whole repo
 - src/backend contains libNXT's code
 - src/utils is utility code that we don't want in libNXT

This commit also changes all includes to use global paths from src/
bacause it had to touch a bunch of #include statements anyway.

src/backend/BindGroupLayout.cpp

@@ -0,0 +1,141 @@
+// Copyright 2017 The NXT 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 "backend/BindGroupLayout.h"
+
+#include "backend/Device.h"
+
+#include <functional>
+
+namespace backend {
+
+    namespace {
+
+        // Workaround for Chrome's stdlib having a broken std::hash for enums and bitsets
+        template<typename T>
+        typename std::enable_if<std::is_enum<T>::value, size_t>::type Hash(T value) {
+            using Integral = typename nxt::UnderlyingType<T>::type;
+            return std::hash<Integral>()(static_cast<Integral>(value));
+        }
+
+        template<size_t N>
+        size_t Hash(const std::bitset<N>& value) {
+            static_assert(N <= sizeof(unsigned long long) * 8, "");
+            return std::hash<unsigned long long>()(value.to_ullong());
+        }
+
+
+        // TODO(cwallez@chromium.org): see if we can use boost's hash combined or some equivalent
+        // this currently assumes that size_t is 64 bits
+        void CombineHashes(size_t* h1, size_t h2) {
+            *h1 ^= (h2 << 7) + (h2 >> (64 - 7)) + 0x304975;
+        }
+
+        size_t HashBindingInfo(const BindGroupLayoutBase::LayoutBindingInfo& info) {
+            size_t hash = Hash(info.mask);
+
+            for (size_t binding = 0; binding < kMaxBindingsPerGroup; ++binding) {
+                if (info.mask[binding]) {
+                    CombineHashes(&hash, Hash(info.visibilities[binding]));
+                    CombineHashes(&hash, Hash(info.types[binding]));
+                }
+            }
+
+            return hash;
+        }
+
+        bool operator== (const BindGroupLayoutBase::LayoutBindingInfo& a, const BindGroupLayoutBase::LayoutBindingInfo& b) {
+            if (a.mask != b.mask) {
+                return false;
+            }
+
+            for (size_t binding = 0; binding < kMaxBindingsPerGroup; ++binding) {
+                if (a.mask[binding]) {
+                    if (a.visibilities[binding] != b.visibilities[binding]) {
+                        return false;
+                    }
+                    if (a.types[binding] != b.types[binding]) {
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        }
+    }
+
+    // BindGroupLayoutBase
+
+    BindGroupLayoutBase::BindGroupLayoutBase(BindGroupLayoutBuilder* builder, bool blueprint)
+        : device(builder->device), bindingInfo(builder->bindingInfo), blueprint(blueprint) {
+    }
+
+    BindGroupLayoutBase::~BindGroupLayoutBase() {
+        // Do not register the actual cached object if we are a blueprint
+        if (!blueprint) {
+            device->UncacheBindGroupLayout(this);
+        }
+    }
+
+    const BindGroupLayoutBase::LayoutBindingInfo& BindGroupLayoutBase::GetBindingInfo() const {
+        return bindingInfo;
+    }
+
+    // BindGroupLayoutBuilder
+
+    BindGroupLayoutBuilder::BindGroupLayoutBuilder(DeviceBase* device) : Builder(device) {
+    }
+
+    const BindGroupLayoutBase::LayoutBindingInfo& BindGroupLayoutBuilder::GetBindingInfo() const {
+        return bindingInfo;
+    }
+
+    BindGroupLayoutBase* BindGroupLayoutBuilder::GetResultImpl() {
+        BindGroupLayoutBase blueprint(this, true);
+
+        auto* result = device->GetOrCreateBindGroupLayout(&blueprint, this);
+        result->Reference();
+        return result;
+    }
+
+    void BindGroupLayoutBuilder::SetBindingsType(nxt::ShaderStageBit visibility, nxt::BindingType bindingType, uint32_t start, uint32_t count) {
+        if (start + count > kMaxBindingsPerGroup) {
+            HandleError("Setting bindings type over maximum number of bindings");
+            return;
+        }
+        for (size_t i = start; i < start + count; i++) {
+            if (bindingInfo.mask[i]) {
+                HandleError("Setting already set binding type");
+                return;
+            }
+        }
+
+        for (size_t i = start; i < start + count; i++) {
+            bindingInfo.mask.set(i);
+            bindingInfo.visibilities[i] = visibility;
+            bindingInfo.types[i] = bindingType;
+        }
+    }
+
+    // BindGroupLayoutCacheFuncs
+
+    size_t BindGroupLayoutCacheFuncs::operator() (const BindGroupLayoutBase* bgl) const {
+        return HashBindingInfo(bgl->GetBindingInfo());
+    }
+
+    bool BindGroupLayoutCacheFuncs::operator() (const BindGroupLayoutBase* a, const BindGroupLayoutBase* b) const {
+        return a->GetBindingInfo() == b->GetBindingInfo();
+    }
+
+}