add TRACE_EVENT to ANGLE (reland)

Tracing code the same as previous CL:
https://codereview.appspot.com/12699047/

Setup code simplified, and follows the GetProcAddress model of other
gl functions.

R=shannonwoods@google.com
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 4cd41af..fcb6315 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -39,6 +39,7 @@
  Adrienne Walker
  thestig@chromium.org
  Justin Schuh
+ Scott Graham
 
 Adobe Systems Inc.
  Alexandru Chiculita
diff --git a/src/build_angle.gypi b/src/build_angle.gypi
index 5016f47..948c024 100644
--- a/src/build_angle.gypi
+++ b/src/build_angle.gypi
@@ -236,11 +236,14 @@
           'sources': [
             'third_party/murmurhash/MurmurHash3.h',
             'third_party/murmurhash/MurmurHash3.cpp',
+            'third_party/trace_event/trace_event.h',
             'common/angleutils.h',
             'common/debug.cpp',
             'common/debug.h',
             'common/mathutil.cpp',
             'common/mathutil.h',
+            'common/event_tracer.cpp',
+            'common/event_tracer.h',
             'common/RefCountObject.cpp',
             'common/RefCountObject.h',
             'common/utilities.cpp',
diff --git a/src/common/event_tracer.cpp b/src/common/event_tracer.cpp
new file mode 100644
index 0000000..96cbb01
--- /dev/null
+++ b/src/common/event_tracer.cpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2012 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "common/event_tracer.h"
+
+namespace gl
+{
+
+GetCategoryEnabledFlagFunc g_getCategoryEnabledFlag;
+AddTraceEventFunc g_addTraceEvent;
+
+}  // namespace gl
+
+extern "C" {
+
+void __stdcall SetTraceFunctionPointers(GetCategoryEnabledFlagFunc getCategoryEnabledFlag,
+                                        AddTraceEventFunc addTraceEvent)
+{
+    gl::g_getCategoryEnabledFlag = getCategoryEnabledFlag;
+    gl::g_addTraceEvent = addTraceEvent;
+}
+
+}  // extern "C"
+
+namespace gl
+{
+
+const unsigned char* TraceGetTraceCategoryEnabledFlag(const char* name)
+{
+    if (g_getCategoryEnabledFlag)
+    {
+        return g_getCategoryEnabledFlag(name);
+    }
+    static unsigned char disabled = 0;
+    return &disabled;
+}
+
+void TraceAddTraceEvent(char phase, const unsigned char* categoryGroupEnabled, const char* name, unsigned long long id,
+                        int numArgs, const char** argNames, const unsigned char* argTypes,
+                        const unsigned long long* argValues, unsigned char flags)
+{
+    if (g_addTraceEvent)
+    {
+        g_addTraceEvent(phase, categoryGroupEnabled, name, id, numArgs, argNames, argTypes, argValues, flags);
+    }
+}
+
+}  // namespace gl
diff --git a/src/common/event_tracer.h b/src/common/event_tracer.h
new file mode 100644
index 0000000..ae397e7
--- /dev/null
+++ b/src/common/event_tracer.h
@@ -0,0 +1,33 @@
+// Copyright (c) 2012 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMMON_EVENT_TRACER_H_
+#define COMMON_EVENT_TRACER_H_
+
+extern "C" {
+
+typedef const unsigned char* (*GetCategoryEnabledFlagFunc)(const char* name);
+typedef void (*AddTraceEventFunc)(char phase, const unsigned char* categoryGroupEnabled, const char* name,
+                                  unsigned long long id, int numArgs, const char** argNames,
+                                  const unsigned char* argTypes, const unsigned long long* argValues,
+                                  unsigned char flags);
+
+// extern "C" so that it has a reasonable name for GetProcAddress.
+void __stdcall SetTraceFunctionPointers(GetCategoryEnabledFlagFunc get_category_enabled_flag,
+                                        AddTraceEventFunc add_trace_event_func);
+
+}
+
+namespace gl
+{
+
+const unsigned char* TraceGetTraceCategoryEnabledFlag(const char* name);
+
+void TraceAddTraceEvent(char phase, const unsigned char* categoryGroupEnabled, const char* name, unsigned long long id,
+                        int numArgs, const char** argNames, const unsigned char* argTypes,
+                        const unsigned long long* argValues, unsigned char flags);
+
+}
+
+#endif  // COMMON_EVENT_TRACER_H_
diff --git a/src/common/version.h b/src/common/version.h
index 98c6dc2..281ff8b 100644
--- a/src/common/version.h
+++ b/src/common/version.h
@@ -1,7 +1,7 @@
 #define MAJOR_VERSION 2
 #define MINOR_VERSION 0
 #define BUILD_VERSION 0
-#define BUILD_REVISION 2007
+#define BUILD_REVISION 2008
 
 #define STRINGIFY(x) #x
 #define MACRO_STRINGIFY(x) STRINGIFY(x)
diff --git a/src/libGLESv2/libGLESv2.def b/src/libGLESv2/libGLESv2.def
index 5d184d2..2b92156 100644
--- a/src/libGLESv2/libGLESv2.def
+++ b/src/libGLESv2/libGLESv2.def
@@ -288,4 +288,7 @@
     glGetProcAddress                @148 NONAME
     glBindTexImage                  @158 NONAME
     glCreateRenderer                @177 NONAME
-    glDestroyRenderer               @178 NONAME
\ No newline at end of file
+    glDestroyRenderer               @178 NONAME
+
+    ; Setting up TRACE macro callbacks
+    SetTraceFunctionPointers        @284
diff --git a/src/libGLESv2/libGLESv2.vcxproj b/src/libGLESv2/libGLESv2.vcxproj
index 339ede7..94bc7eb 100644
--- a/src/libGLESv2/libGLESv2.vcxproj
+++ b/src/libGLESv2/libGLESv2.vcxproj
@@ -85,7 +85,7 @@
     <ClCompile>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/..; $(ProjectDir)/../../include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;_USRDLL;LIBGLESV2_EXPORTS;_CRT_SECURE_NO_DEPRECATE;NOMINMAX;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;_USRDLL;LIBGLESV2_EXPORTS;_CRT_SECURE_NO_DEPRECATE;NOMINMAX;ANGLE_IMPLEMENTATION;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <MinimalRebuild>true</MinimalRebuild>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
@@ -120,7 +120,7 @@
       <Optimization>MaxSpeed</Optimization>
       <InlineFunctionExpansion>AnySuitable</InlineFunctionExpansion>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/..; $(ProjectDir)/../../include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>ANGLE_DISABLE_TRACE;WIN32;NDEBUG;_WINDOWS;_USRDLL;LIBGLESV2_EXPORTS;_CRT_SECURE_NO_DEPRECATE;NOMINMAX;_SECURE_SCL=0;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ANGLE_DISABLE_TRACE;WIN32;NDEBUG;_WINDOWS;_USRDLL;LIBGLESV2_EXPORTS;_CRT_SECURE_NO_DEPRECATE;NOMINMAX;_SECURE_SCL=0;ANGLE_IMPLEMENTATION;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <PrecompiledHeader>Use</PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
@@ -250,6 +250,12 @@
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">NotUsing</PrecompiledHeader>
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|x64'">NotUsing</PrecompiledHeader>
     </ClCompile>
+    <ClCompile Include="..\common\event_tracer.cpp">
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">NotUsing</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">NotUsing</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">NotUsing</PrecompiledHeader>
+      <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|x64'">NotUsing</PrecompiledHeader>
+    </ClCompile>
     <ClCompile Include="Fence.cpp" />
     <ClCompile Include="Float16ToFloat32.cpp" />
     <ClCompile Include="formatutils.cpp" />
@@ -333,10 +339,12 @@
     <ClInclude Include="..\..\include\GLES3\gl3platform.h" />
     <ClInclude Include="..\common\angleutils.h" />
     <ClInclude Include="..\common\debug.h" />
+    <ClInclude Include="..\common\event_tracer.h" />
     <ClInclude Include="..\common\mathutil.h" />
     <ClInclude Include="..\common\system.h" />
     <ClInclude Include="..\common\utilities.h" />
     <ClInclude Include="..\third_party\murmurhash\MurmurHash3.h" />
+    <ClInclude Include="..\third_party\trace_event\trace_event.h" />
     <ClInclude Include="angletypes.h" />
     <ClInclude Include="BinaryStream.h" />
     <ClInclude Include="Buffer.h" />
@@ -495,3 +503,4 @@
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
 </Project>
+
diff --git a/src/libGLESv2/libGLESv2.vcxproj.filters b/src/libGLESv2/libGLESv2.vcxproj.filters
index ba8ea39..a018c21 100644
--- a/src/libGLESv2/libGLESv2.vcxproj.filters
+++ b/src/libGLESv2/libGLESv2.vcxproj.filters
@@ -39,6 +39,9 @@
     <Filter Include="Source Files\Renderer11">
       <UniqueIdentifier>{72db61d3-e081-4b58-bc63-a04a8a70585f}</UniqueIdentifier>
     </Filter>
+    <Filter Include="Third Party\trace_event">
+      <UniqueIdentifier>{ebfc1614-8f0b-48c7-b6bd-295bf91ef85c}</UniqueIdentifier>
+    </Filter>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="Buffer.cpp">
@@ -248,6 +251,9 @@
     <ClCompile Include="renderer\IndexRangeCache.cpp">
       <Filter>Source Files\Renderer</Filter>
     </ClCompile>
+    <ClCompile Include="..\common\event_tracer.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
     <ClCompile Include="RenderbufferProxySet.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
@@ -541,9 +547,15 @@
     <ClInclude Include="renderer\IndexRangeCache.h">
       <Filter>Header Files\Renderer</Filter>
     </ClInclude>
-    <ClInclude Include="RenderbufferProxySet.h">
+    <ClInclude Include="renderer\IndexRangeCache.h">
+      <Filter>Header Files\Renderer</Filter>
+    </ClInclude>
+    <ClInclude Include="..\common\event_tracer.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\third_party\trace_event\trace_event.h">
+      <Filter>Third Party\trace_event</Filter>
+    </ClInclude>
     <ClInclude Include="validationES2.h">
       <Filter>Header Files</Filter>
     </ClInclude>
diff --git a/src/libGLESv2/renderer/Renderer.cpp b/src/libGLESv2/renderer/Renderer.cpp
index e045881..69330ae 100644
--- a/src/libGLESv2/renderer/Renderer.cpp
+++ b/src/libGLESv2/renderer/Renderer.cpp
@@ -14,6 +14,7 @@
 #include "libGLESv2/renderer/Renderer9.h"
 #include "libGLESv2/renderer/Renderer11.h"
 #include "common/utilities.h"
+#include "third_party/trace_event/trace_event.h"
 
 #if !defined(ANGLE_ENABLE_D3D11)
 // Enables use of the Direct3D 11 API for a default display, when available
@@ -41,6 +42,7 @@
 
 bool Renderer::initializeCompiler()
 {
+    TRACE_EVENT0("gpu", "initializeCompiler");
 #if defined(ANGLE_PRELOADED_D3DCOMPILER_MODULE_NAMES)
     // Find a D3DCompiler module that had already been loaded based on a predefined list of versions.
     static TCHAR* d3dCompilerNames[] = ANGLE_PRELOADED_D3DCOMPILER_MODULE_NAMES;
diff --git a/src/libGLESv2/renderer/Renderer9.cpp b/src/libGLESv2/renderer/Renderer9.cpp
index 27867bc..506c223 100644
--- a/src/libGLESv2/renderer/Renderer9.cpp
+++ b/src/libGLESv2/renderer/Renderer9.cpp
@@ -33,6 +33,8 @@
 
 #include "libEGL/Display.h"
 
+#include "third_party/trace_event/trace_event.h"
+
 // Can also be enabled by defining FORCE_REF_RAST in the project's predefined macros
 #define REF_RAST 0
 
@@ -171,10 +173,12 @@
 
     if (mSoftwareDevice)
     {
+        TRACE_EVENT0("gpu", "GetModuleHandle_swiftshader");
         mD3d9Module = GetModuleHandle(TEXT("swiftshader_d3d9.dll"));
     }
     else
     {
+        TRACE_EVENT0("gpu", "GetModuleHandle_d3d9");
         mD3d9Module = GetModuleHandle(TEXT("d3d9.dll"));
     }
 
@@ -192,12 +196,14 @@
     // desktop. Direct3D9Ex is available in Windows Vista and later if suitable drivers are available.
     if (ANGLE_ENABLE_D3D9EX && Direct3DCreate9ExPtr && SUCCEEDED(Direct3DCreate9ExPtr(D3D_SDK_VERSION, &mD3d9Ex)))
     {
+        TRACE_EVENT0("gpu", "D3d9Ex_QueryInterface");
         ASSERT(mD3d9Ex);
         mD3d9Ex->QueryInterface(IID_IDirect3D9, reinterpret_cast<void**>(&mD3d9));
         ASSERT(mD3d9);
     }
     else
     {
+        TRACE_EVENT0("gpu", "Direct3DCreate9");
         mD3d9 = Direct3DCreate9(D3D_SDK_VERSION);
     }
 
@@ -215,21 +221,24 @@
     HRESULT result;
 
     // Give up on getting device caps after about one second.
-    for (int i = 0; i < 10; ++i)
     {
-        result = mD3d9->GetDeviceCaps(mAdapter, mDeviceType, &mDeviceCaps);
-        if (SUCCEEDED(result))
+        TRACE_EVENT0("gpu", "GetDeviceCaps");
+        for (int i = 0; i < 10; ++i)
         {
-            break;
-        }
-        else if (result == D3DERR_NOTAVAILABLE)
-        {
-            Sleep(100);   // Give the driver some time to initialize/recover
-        }
-        else if (FAILED(result))   // D3DERR_OUTOFVIDEOMEMORY, E_OUTOFMEMORY, D3DERR_INVALIDDEVICE, or another error we can't recover from
-        {
-            ERR("failed to get device caps (0x%x)\n", result);
-            return EGL_NOT_INITIALIZED;
+            result = mD3d9->GetDeviceCaps(mAdapter, mDeviceType, &mDeviceCaps);
+            if (SUCCEEDED(result))
+            {
+                break;
+            }
+            else if (result == D3DERR_NOTAVAILABLE)
+            {
+                Sleep(100);   // Give the driver some time to initialize/recover
+            }
+            else if (FAILED(result))   // D3DERR_OUTOFVIDEOMEMORY, E_OUTOFMEMORY, D3DERR_INVALIDDEVICE, or another error we can't recover from
+            {
+                ERR("failed to get device caps (0x%x)\n", result);
+                return EGL_NOT_INITIALIZED;
+            }
         }
     }
 
@@ -247,7 +256,10 @@
         return EGL_NOT_INITIALIZED;
     }
 
-    mD3d9->GetAdapterIdentifier(mAdapter, 0, &mAdapterIdentifier);
+    {
+        TRACE_EVENT0("gpu", "GetAdapterIdentifier");
+        mD3d9->GetAdapterIdentifier(mAdapter, 0, &mAdapterIdentifier);
+    }
 
     // ATI cards on XP have problems with non-power-of-two textures.
     mSupportsNonPower2Textures = !(mDeviceCaps.TextureCaps & D3DPTEXTURECAPS_POW2) &&
@@ -292,6 +304,7 @@
     const d3d9::D3DFormatSet &d3d9Formats = d3d9::GetAllUsedD3DFormats();
     for (d3d9::D3DFormatSet::const_iterator i = d3d9Formats.begin(); i != d3d9Formats.end(); ++i)
     {
+        TRACE_EVENT0("gpu", "getMultiSampleSupport");
         MultisampleSupportInfo support = getMultiSampleSupport(*i);
         mMultiSampleSupport[*i] = support;
         mMaxSupportedSamples = std::max(mMaxSupportedSamples, support.maxSupportedSamples);
@@ -300,12 +313,18 @@
     static const TCHAR windowName[] = TEXT("AngleHiddenWindow");
     static const TCHAR className[] = TEXT("STATIC");
 
-    mDeviceWindow = CreateWindowEx(WS_EX_NOACTIVATE, className, windowName, WS_DISABLED | WS_POPUP, 0, 0, 1, 1, HWND_MESSAGE, NULL, GetModuleHandle(NULL), NULL);
+    {
+        TRACE_EVENT0("gpu", "CreateWindowEx");
+        mDeviceWindow = CreateWindowEx(WS_EX_NOACTIVATE, className, windowName, WS_DISABLED | WS_POPUP, 0, 0, 1, 1, HWND_MESSAGE, NULL, GetModuleHandle(NULL), NULL);
+    }
 
     D3DPRESENT_PARAMETERS presentParameters = getDefaultPresentParameters();
     DWORD behaviorFlags = D3DCREATE_FPU_PRESERVE | D3DCREATE_NOWINDOWCHANGES;
 
-    result = mD3d9->CreateDevice(mAdapter, mDeviceType, mDeviceWindow, behaviorFlags | D3DCREATE_HARDWARE_VERTEXPROCESSING | D3DCREATE_PUREDEVICE, &presentParameters, &mDevice);
+    {
+        TRACE_EVENT0("gpu", "D3d9_CreateDevice");
+        result = mD3d9->CreateDevice(mAdapter, mDeviceType, mDeviceWindow, behaviorFlags | D3DCREATE_HARDWARE_VERTEXPROCESSING | D3DCREATE_PUREDEVICE, &presentParameters, &mDevice);
+    }
     if (result == D3DERR_OUTOFVIDEOMEMORY || result == E_OUTOFMEMORY || result == D3DERR_DEVICELOST)
     {
         return EGL_BAD_ALLOC;
@@ -313,6 +332,7 @@
 
     if (FAILED(result))
     {
+        TRACE_EVENT0("gpu", "D3d9_CreateDevice2");
         result = mD3d9->CreateDevice(mAdapter, mDeviceType, mDeviceWindow, behaviorFlags | D3DCREATE_SOFTWARE_VERTEXPROCESSING, &presentParameters, &mDevice);
 
         if (FAILED(result))
@@ -324,35 +344,45 @@
 
     if (mD3d9Ex)
     {
+        TRACE_EVENT0("gpu", "mDevice_QueryInterface");
         result = mDevice->QueryInterface(IID_IDirect3DDevice9Ex, (void**) &mDeviceEx);
         ASSERT(SUCCEEDED(result));
     }
 
-    mVertexShaderCache.initialize(mDevice);
-    mPixelShaderCache.initialize(mDevice);
+    {
+        TRACE_EVENT0("gpu", "ShaderCache initialize");
+        mVertexShaderCache.initialize(mDevice);
+        mPixelShaderCache.initialize(mDevice);
+    }
 
     // Check occlusion query support
     IDirect3DQuery9 *occlusionQuery = NULL;
-    if (SUCCEEDED(mDevice->CreateQuery(D3DQUERYTYPE_OCCLUSION, &occlusionQuery)) && occlusionQuery)
     {
-        SafeRelease(occlusionQuery);
-        mOcclusionQuerySupport = true;
-    }
-    else
-    {
-        mOcclusionQuerySupport = false;
+        TRACE_EVENT0("gpu", "device_CreateQuery");
+        if (SUCCEEDED(mDevice->CreateQuery(D3DQUERYTYPE_OCCLUSION, &occlusionQuery)) && occlusionQuery)
+        {
+            SafeRelease(occlusionQuery);
+            mOcclusionQuerySupport = true;
+        }
+        else
+        {
+            mOcclusionQuerySupport = false;
+        }
     }
 
     // Check event query support
     IDirect3DQuery9 *eventQuery = NULL;
-    if (SUCCEEDED(mDevice->CreateQuery(D3DQUERYTYPE_EVENT, &eventQuery)) && eventQuery)
     {
-        SafeRelease(eventQuery);
-        mEventQuerySupport = true;
-    }
-    else
-    {
-        mEventQuerySupport = false;
+        TRACE_EVENT0("gpu", "device_CreateQuery2");
+        if (SUCCEEDED(mDevice->CreateQuery(D3DQUERYTYPE_EVENT, &eventQuery)) && eventQuery)
+        {
+            SafeRelease(eventQuery);
+            mEventQuerySupport = true;
+        }
+        else
+        {
+            mEventQuerySupport = false;
+        }
     }
 
     D3DDISPLAYMODE currentDisplayMode;
diff --git a/src/third_party/trace_event/trace_event.h b/src/third_party/trace_event/trace_event.h
new file mode 100644
index 0000000..1880056
--- /dev/null
+++ b/src/third_party/trace_event/trace_event.h
@@ -0,0 +1,826 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// 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 COMMON_TRACE_EVENT_H_
+#define COMMON_TRACE_EVENT_H_
+
+#include <string>
+
+#include "common/event_tracer.h"
+
+// 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(category, name) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name)
+#define TRACE_EVENT1(category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val)
+#define TRACE_EVENT2(category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(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(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_INSTANT1(category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_INSTANT0(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_INSTANT1(category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_INSTANT2(category, name, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(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(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_BEGIN1(category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_BEGIN2(category, name, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
+#define TRACE_EVENT_COPY_BEGIN0(category, name) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_BEGIN1(category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_BEGIN2(category, name, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD(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(category, name, value) \
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
+        category, name, TRACE_EVENT_FLAG_NONE, \
+        "value", static_cast<int>(value))
+#define TRACE_COPY_COUNTER1(category, name, value) \
+    INTERNAL_TRACE_EVENT_ADD(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(category, name, value1_name, value1_val, \
+        value2_name, value2_val) \
+    INTERNAL_TRACE_EVENT_ADD(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(category, name, value1_name, value1_val, \
+        value2_name, value2_val) \
+    INTERNAL_TRACE_EVENT_ADD(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(category, name, id, value) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
+        category, name, id, TRACE_EVENT_FLAG_NONE, \
+        "value", static_cast<int>(value))
+#define TRACE_COPY_COUNTER_ID1(category, name, id, value) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id, value1_name, value1_val, \
+        value2_name, value2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id, value1_name, value1_val, \
+        value2_name, value2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
+        category, name, id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
+        category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
+        category, name, id, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
+        category, name, id, TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id, step) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
+        category, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
+#define TRACE_EVENT_ASYNC_STEP1(category, name, id, step, \
+                                      arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
+        category, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
+        arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_STEP0(category, name, id, step) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
+        category, name, id, TRACE_EVENT_FLAG_COPY, "step", step)
+#define TRACE_EVENT_COPY_ASYNC_STEP1(category, name, id, step, \
+        arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
+        category, name, id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
+        category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(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(category, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
+        category, name, id, TRACE_EVENT_FLAG_COPY)
+#define TRACE_EVENT_COPY_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
+        category, name, id, TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val)
+#define TRACE_EVENT_COPY_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
+        arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
+        category, 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 \
+    gl::TraceGetTraceCategoryEnabledFlag
+
+// 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 \
+    gl::TraceAddTraceEvent
+
+////////////////////////////////////////////////////////////////////////////////
+
+// 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(category) \
+    static const unsigned char* INTERNALTRACEEVENTUID(catstatic) = 0; \
+    if (!INTERNALTRACEEVENTUID(catstatic)) \
+      INTERNALTRACEEVENTUID(catstatic) = \
+          TRACE_EVENT_API_GET_CATEGORY_ENABLED(category);
+
+// Implementation detail: internal macro to create static category and add
+// event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_ADD(phase, category, name, flags, ...) \
+    do { \
+        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
+        if (*INTERNALTRACEEVENTUID(catstatic)) { \
+            gl::TraceEvent::addTraceEvent( \
+                phase, INTERNALTRACEEVENTUID(catstatic), name, \
+                gl::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(category, name, ...) \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
+    gl::TraceEvent::TraceEndOnScopeClose \
+        INTERNALTRACEEVENTUID(profileScope); \
+    if (*INTERNALTRACEEVENTUID(catstatic)) { \
+      gl::TraceEvent::addTraceEvent( \
+          TRACE_EVENT_PHASE_BEGIN, \
+          INTERNALTRACEEVENTUID(catstatic), \
+          name, gl::TraceEvent::noEventId, \
+          TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
+      INTERNALTRACEEVENTUID(profileScope).initialize( \
+          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(phase, category, name, id, flags, \
+                                         ...) \
+    do { \
+        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
+        if (*INTERNALTRACEEVENTUID(catstatic)) { \
+            unsigned char traceEventFlags = flags | TRACE_EVENT_FLAG_HAS_ID; \
+            gl::TraceEvent::TraceID traceEventTraceID( \
+                id, &traceEventFlags); \
+            gl::TraceEvent::addTraceEvent( \
+                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_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 gl {
+
+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<unsigned long>(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 void addTraceEvent(char phase,
+                                const unsigned char* categoryEnabled,
+                                const char* name,
+                                unsigned long long id,
+                                unsigned char flags) {
+    TRACE_EVENT_API_ADD_TRACE_EVENT(
+        phase, categoryEnabled, name, id,
+        zeroNumArgs, 0, 0, 0,
+        flags);
+}
+
+template<class ARG1_TYPE>
+static inline void addTraceEvent(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];
+    unsigned long long argValues[1];
+    setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
+    TRACE_EVENT_API_ADD_TRACE_EVENT(
+        phase, categoryEnabled, name, id,
+        numArgs, &arg1Name, argTypes, argValues,
+        flags);
+}
+
+template<class ARG1_TYPE, class ARG2_TYPE>
+static inline void addTraceEvent(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];
+    unsigned long long argValues[2];
+    setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
+    setTraceValue(arg2Val, &argTypes[1], &argValues[1]);
+    return TRACE_EVENT_API_ADD_TRACE_EVENT(
+        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(const unsigned char* categoryEnabled,
+                    const char* name)
+    {
+        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(
+                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 {
+        const unsigned char* categoryEnabled;
+        const char* name;
+    };
+    Data* m_pdata;
+    Data m_data;
+};
+
+// TraceEventSamplingStateScope records the current sampling state
+// and sets a new sampling state. When the scope exists, it restores
+// the sampling state having recorded.
+template<size_t BucketNumber>
+class SamplingStateScope {
+public:
+    SamplingStateScope(const char* categoryAndName)
+    {
+        m_previousState = SamplingStateScope<BucketNumber>::current();
+        SamplingStateScope<BucketNumber>::set(categoryAndName);
+    }
+
+    ~SamplingStateScope()
+    {
+        SamplingStateScope<BucketNumber>::set(m_previousState);
+    }
+
+    // FIXME: Make load/store to traceSamplingState[] thread-safe and atomic.
+    static inline const char* current()
+    {
+        return reinterpret_cast<const char*>(*gl::traceSamplingState[BucketNumber]);
+    }
+    static inline void set(const char* categoryAndName)
+    {
+        *gl::traceSamplingState[BucketNumber] = reinterpret_cast<long>(const_cast<char*>(categoryAndName));
+    }
+
+private:
+    const char* m_previousState;
+};
+
+} // namespace TraceEvent
+
+} // namespace gl
+
+#endif