Add a sampling tracing to RenderWidget::DoDeferredUpdate

base/debug/trace_event_unittest.cc

Index: base/debug/trace_event_unittest.cc
diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 000097e16e0c58f739cf9376d955ef58bf728261..401aa4f8ba5cf96fc62261912b95b755e976ca38 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -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_SAMPLING_STATE0("cc", "Stuff");
   sampled->Wait();
-  TRACE_EVENT_SAMPLE_STATE(1, "cc", "Things");
+  TRACE_EVENT_SAMPLING_STATE0("cc", "Things");
   sampled->Wait();
 
   EndTraceAndFlush();
@@ -1815,6 +1815,49 @@ TEST_F(TraceEventTestFixture, TraceSampling) {
 }
 #endif  // !CHROME_SPLIT_DLL
 
+// Not supported in split dll build. http://crbug.com/237249
+#if !defined(CHROME_SPLIT_DLL)
+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);
+
+  TraceEventSamplingState0Scope scope("AAA");
+  sampled->Wait();
+  {
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "AAA");
+      TraceEventSamplingState0Scope scope2("BBB");
+      sampled->Wait();
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "BBB");
+  }
+  sampled->Wait();
+  {
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "AAA");
+      TraceEventSamplingState0Scope scope2("CCC");
+      sampled->Wait();
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "CCC");
+  }
+  sampled->Wait();
+  {
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "AAA");
+      TraceEventSamplingState0Scope::forceCurrent("DDD");
+      sampled->Wait();
+      EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "DDD");
+  }
+  sampled->Wait();
+  EXPECT_STREQ(TraceEventSamplingState0Scope::current(), "DDD");
+
+  EndTraceAndFlush();
+}
+#endif  // !CHROME_SPLIT_DLL
+
 class MyData : public base::debug::ConvertableToTraceFormat {
  public:
   MyData() {}