Move and rename TaskTimeTracker to public interface exposed to WebThread, use in WebPerf Agent.

third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h
index 7e84e40b8ce5d69bdb2427ac808e5c71d67ed890..ef8c7cdc00df85b7ea9289cdaa57bd9e5c958949 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.h
@@ -83,17 +83,12 @@ class BLINK_PLATFORM_EXPORT TaskQueueManager
   // tasks posted to the main loop. The batch size is 1 by default.
   void SetWorkBatchSize(int work_batch_size);
 
-  // When given a non-null TaskTimeTracker, the TaskQueueManager calls its
-  // ReportTaskTime method for every top level task. The task_time_tracker must
-  // outlive this object, or be removed via SetTaskTimeTracker(nullptr).
-  void SetTaskTimeTracker(TaskTimeTracker* task_time_tracker) {
-    task_time_tracker_ = task_time_tracker;
-  }
-
   // These functions can only be called on the same thread that the task queue
   // manager executes its tasks on.
   void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer);
   void RemoveTaskObserver(base::MessageLoop::TaskObserver* task_observer);
+  void AddTaskTimeTracker(TaskTimeTracker* task_time_tracker);

[Sami, 2016/08/23 10:34:59]

naming bikeshed: Should we rename this to TaskTimeObserver for consistency?

[panicker, 2016/08/23 18:08:23]

Sure, I'm fine with that.
Although I'd prefer to make the naming change after addressing all other review
comments.

+  void RemoveTaskTimeTracker(TaskTimeTracker* task_time_tracker);
 
   // Returns true if any task from a monitored task queue was was run since the
   // last call to GetAndClearSystemIsQuiescentBit.
@@ -248,7 +243,7 @@ class BLINK_PLATFORM_EXPORT TaskQueueManager
 
   base::ObserverList<base::MessageLoop::TaskObserver> task_observers_;
 
-  TaskTimeTracker* task_time_tracker_;  // NOT OWNED
+  base::ObserverList<TaskTimeTracker> task_time_trackers_;
 
   const char* tracing_category_;
   const char* disabled_by_default_tracing_category_;