Record task durations on Renderer Main & Compositor threads.

base/tracked_objects.h

Index: base/tracked_objects.h
diff --git a/base/tracked_objects.h b/base/tracked_objects.h
index b3aed63434e827b5bb46ac3046dd888536863e11..f429deb36cad51c08ab4f294264ba88ca71b395d 100644
--- a/base/tracked_objects.h
+++ b/base/tracked_objects.h
@@ -622,6 +622,12 @@ class BASE_EXPORT ThreadData {
     return sanitized_thread_name_;
   }
 
+  void EnableTaskDurationRecordingForUMA();
+  // Whether this thread records task lengths for UMA.
+  bool task_length_recording_enabled_for_uma() const {
+    return task_length_recording_enabled_for_uma_;
+  };
+
   // Initializes all statics if needed (this initialization call should be made
   // while we are single threaded).
   static void EnsureTlsInitialization();
@@ -646,6 +652,10 @@ class BASE_EXPORT ThreadData {
   // the code).
   static base::TimeTicks Now();
 
+  // If the provided thread is enabled for task duration tracking, returns the

[Sami, 2017/07/26 20:36:38]

nit: "UMA task duration tracking" (I had to re-read this a couple of times to
figure out the difference to Now())

+  // current time. Otherwise, this is equivalent to Now().
+  static base::TimeTicks Now(const ThreadData* thread_data);
+
   // This function can be called at process termination to validate that thread
   // cleanup routines have been called for at least some number of named
   // threads.
@@ -823,6 +833,8 @@ class BASE_EXPORT ThreadData {
   // if it exists; NULL otherwise.
   TaskStopwatch* current_stopwatch_;
 
+  bool task_length_recording_enabled_for_uma_;
+
   DISALLOW_COPY_AND_ASSIGN(ThreadData);
 };