Add trace code to track all posted tasks in message_loop.

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 3fbc777203e7fbfc56c9abefc56fd7a4de0b5617..f42fbf790f19fc37fce0e514eb01dd78f7dc1fa8 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -44,9 +44,11 @@ class TraceEventTestFixture : public testing::Test {
  private:
   // We want our singleton torn down after each test.
   ShadowingAtExitManager at_exit_manager_;
+  Lock lock_;
 };
 
 void TraceEventTestFixture::ManualTestSetUp() {
+  TraceLog::DeleteForTesting();
   TraceLog::Resurrect();
   TraceLog* tracelog = TraceLog::GetInstance();
   ASSERT_TRUE(tracelog);
@@ -58,6 +60,7 @@ void TraceEventTestFixture::ManualTestSetUp() {
 
 void TraceEventTestFixture::OnTraceDataCollected(
     scoped_refptr<TraceLog::RefCountedString> json_events_str) {
+  AutoLock lock(lock_);
   trace_string_ += json_events_str->data;
 
   scoped_ptr<Value> root;
@@ -529,9 +532,9 @@ TEST_F(TraceEventTestFixture, DataCapturedOnThread) {
     FROM_HERE, NewRunnableFunction(&TraceWithAllMacroVariants,
                                    &task_complete_event));
   task_complete_event.Wait();
+  thread.Stop();
 
   TraceLog::GetInstance()->SetEnabled(false);
-  thread.Stop();
   ValidateAllTraceMacrosCreatedData(trace_parsed_, trace_string_);
 }
 
@@ -557,14 +560,14 @@ TEST_F(TraceEventTestFixture, DataCapturedManyThreads) {
     task_complete_events[i]->Wait();
   }
 
-  TraceLog::GetInstance()->SetEnabled(false);
-
   for (int i = 0; i < num_threads; i++) {
     threads[i]->Stop();
     delete threads[i];
     delete task_complete_events[i];
   }
 
+  TraceLog::GetInstance()->SetEnabled(false);
+
   ValidateInstantEventPresentOnEveryThread(trace_parsed_, trace_string_,
                                            num_threads, num_events);
 }
@@ -600,13 +603,14 @@ TEST_F(TraceEventTestFixture, ThreadNames) {
   }
 
   // Shut things down.
-  TraceLog::GetInstance()->SetEnabled(false);
   for (int i = 0; i < num_threads; i++) {
     threads[i]->Stop();
     delete threads[i];
     delete task_complete_events[i];
   }
 
+  TraceLog::GetInstance()->SetEnabled(false);
+
   std::string tmp;
   int tmp_int;
   DictionaryValue* item;