Add a sampling tracing to RenderWidget::DoDeferredUpdate

- This CL implements TraceEventSamplingState0Scope for scoped sampling. The implementation is the same as TraceEvent.h in Blink.

- This CL renames TRACE_EVENT_SAMPLE_STATE to TRACE_EVENT_SAMPLING_STATE, to make the name consistent with the macros in Blink.

TEST=TraceEventTestFixture.TraceSamplingScope
BUG=241743

Review URL: https://chromiumcodereview.appspot.com/18587004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210160 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 120 insertions, 18 deletions

diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index aa4cc75..c162b39 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -299,10 +299,34 @@
 // 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.
-#define TRACE_EVENT_SAMPLE_STATE(thread_bucket, category, name)                \
-  TRACE_EVENT_API_ATOMIC_STORE(                                                \
-      TRACE_EVENT_API_THREAD_BUCKET(thread_bucket),                            \
-      reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(category "\0" name));
+#define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET( \
+    bucket_number, category, name)                 \
+        trace_event_internal::                     \
+        TraceEventSamplingStateScope<bucket_number>::Set(category "\0" name)
+
+// Returns a current sampling state of the given bucket.
+#define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
+    trace_event_internal::TraceEventSamplingStateScope<bucket_number>::Current()
+
+// Creates a scope of a sampling state of the given bucket.
+//
+// {  // 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)                                      \
+    trace_event_internal::TraceEventSamplingStateScope<bucket_number>   \
+        traceEventSamplingScope(category "\0" name);
+
+// 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)
+
 
 // Records a single BEGIN event called "name" immediately, with 0, 1 or 2
 // associated arguments. If the category is not enabled, then this
@@ -755,14 +779,15 @@
 // Defines visibility for classes in trace_event.h
 #define TRACE_EVENT_API_CLASS_EXPORT BASE_EXPORT
 
-// Not supported in split-dll build. http://crbug.com/237249
+// Not supported in split-dll build. http://crbug.com/256965
 #if !defined(CHROME_SPLIT_DLL)
 // The thread buckets for the sampling profiler.
-TRACE_EVENT_API_CLASS_EXPORT extern TRACE_EVENT_API_ATOMIC_WORD g_trace_state0;
-TRACE_EVENT_API_CLASS_EXPORT extern TRACE_EVENT_API_ATOMIC_WORD g_trace_state1;
-TRACE_EVENT_API_CLASS_EXPORT extern TRACE_EVENT_API_ATOMIC_WORD g_trace_state2;
+TRACE_EVENT_API_CLASS_EXPORT extern \
+    TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
+
 #define TRACE_EVENT_API_THREAD_BUCKET(thread_bucket)                           \
-  g_trace_state##thread_bucket
+    g_trace_state[thread_bucket]
+
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1439,6 +1464,45 @@ class TRACE_EVENT_API_CLASS_EXPORT ScopedTrace {
 #define TRACE_EVENT_BINARY_EFFICIENT0(category_group, name) \
     INTERNAL_TRACE_EVENT_BINARY_EFFICIENT_ADD_SCOPED(category_group, name)
 
+// 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 TraceEventSamplingStateScope {
+ public:
+  TraceEventSamplingStateScope(const char* category_and_name) {
+    previous_state_ = TraceEventSamplingStateScope<BucketNumber>::Current();
+    TraceEventSamplingStateScope<BucketNumber>::Set(category_and_name);
+  }
+
+  ~TraceEventSamplingStateScope() {
+    TraceEventSamplingStateScope<BucketNumber>::Set(previous_state_);
+  }
+
+  static inline const char* Current() {
+// Not supported in split-dll build. http://crbug.com/256965
+#if !defined(CHROME_SPLIT_DLL)
+    return reinterpret_cast<const char*>(TRACE_EVENT_API_ATOMIC_LOAD(
+      g_trace_state[BucketNumber]));
+#else
+    return NULL;
+#endif
+  }
+
+  static inline void Set(const char* category_and_name) {
+// Not supported in split-dll build. http://crbug.com/256965
+#if !defined(CHROME_SPLIT_DLL)
+    TRACE_EVENT_API_ATOMIC_STORE(
+      g_trace_state[BucketNumber],
+      reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(
+        const_cast<char*>(category_and_name)));
+#endif
+  }
+
+ private:
+  const char* previous_state_;
+};
+
 }  // namespace trace_event_internal
 
 namespace base {
diff --git a/base/debug/trace_event_impl.cc b/base/debug/trace_event_impl.cc
index d97c461..27195f9 100644
--- a/base/debug/trace_event_impl.cc
+++ b/base/debug/trace_event_impl.cc
@@ -43,9 +43,7 @@ class DeleteTraceLogForTesting {
 // Not supported in split-dll build. http://crbug.com/237249
 #if !defined(CHROME_SPLIT_DLL)
 // The thread buckets for the sampling profiler.
-BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state0;
-BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state1;
-BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state2;
+BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
 #endif
 
 namespace base {
@@ -948,15 +946,15 @@ void TraceLog::SetEnabled(const CategoryFilter& category_filter,
     if (options & ENABLE_SAMPLING) {
       sampling_thread_.reset(new TraceSamplingThread);
       sampling_thread_->RegisterSampleBucket(
-          &g_trace_state0,
+          &g_trace_state[0],
           "bucket0",
           Bind(&TraceSamplingThread::DefaultSampleCallback));
       sampling_thread_->RegisterSampleBucket(
-          &g_trace_state1,
+          &g_trace_state[1],
           "bucket1",
           Bind(&TraceSamplingThread::DefaultSampleCallback));
       sampling_thread_->RegisterSampleBucket(
-          &g_trace_state2,
+          &g_trace_state[2],
           "bucket2",
           Bind(&TraceSamplingThread::DefaultSampleCallback));
       if (!PlatformThread::Create(
diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 000097e..83f98d2 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -1788,7 +1788,7 @@ TEST_F(TraceEventTestFixture, TraceOptionsParsing) {
                 "record-continuously,enable-sampling"));
 }
 
-// Not supported in split dll build. http://crbug.com/237249
+// Not supported in split dll build. http://crbug.com/256965
 #if !defined(CHROME_SPLIT_DLL)
 TEST_F(TraceEventTestFixture, TraceSampling) {
   ManualTestSetUp();
@@ -1802,9 +1802,9 @@ TEST_F(TraceEventTestFixture, TraceSampling) {
   WaitableEvent* sampled = new WaitableEvent(false, false);
   TraceLog::GetInstance()->InstallWaitableEventForSamplingTesting(sampled);
 
-  TRACE_EVENT_SAMPLE_STATE(1, "cc", "Stuff");
+  TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(1, "cc", "Stuff");
   sampled->Wait();
-  TRACE_EVENT_SAMPLE_STATE(1, "cc", "Things");
+  TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(1, "cc", "Things");
   sampled->Wait();
 
   EndTraceAndFlush();
@@ -1813,6 +1813,46 @@ TEST_F(TraceEventTestFixture, TraceSampling) {
   EXPECT_TRUE(FindNamePhase("Stuff", "P"));
   EXPECT_TRUE(FindNamePhase("Things", "P"));
 }
+
+TEST_F(TraceEventTestFixture, TraceSamplingScope) {
+  ManualTestSetUp();
+
+  event_watch_notification_ = 0;
+  TraceLog::GetInstance()->SetEnabled(
+    CategoryFilter("*"),
+    TraceLog::Options(TraceLog::RECORD_UNTIL_FULL |
+                      TraceLog::ENABLE_SAMPLING));
+
+  WaitableEvent* sampled = new WaitableEvent(false, false);
+  TraceLog::GetInstance()->InstallWaitableEventForSamplingTesting(sampled);
+
+  TRACE_EVENT_SCOPED_SAMPLING_STATE("AAA", "name");
+  sampled->Wait();
+  {
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "AAA");
+    TRACE_EVENT_SCOPED_SAMPLING_STATE("BBB", "name");
+    sampled->Wait();
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "BBB");
+  }
+  sampled->Wait();
+  {
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "AAA");
+    TRACE_EVENT_SCOPED_SAMPLING_STATE("CCC", "name");
+    sampled->Wait();
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "CCC");
+  }
+  sampled->Wait();
+  {
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "AAA");
+    TRACE_EVENT_SET_SAMPLING_STATE("DDD", "name");
+    sampled->Wait();
+    EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "DDD");
+  }
+  sampled->Wait();
+  EXPECT_STREQ(TRACE_EVENT_GET_SAMPLING_STATE(), "DDD");
+
+  EndTraceAndFlush();
+}
 #endif  // !CHROME_SPLIT_DLL
 
 class MyData : public base::debug::ConvertableToTraceFormat {