Force events to be non blocking if main thread is unresponsive.

third_party/WebKit/public/platform/scheduler/base/task_time_observer.h

Index: third_party/WebKit/public/platform/scheduler/base/task_time_observer.h
diff --git a/third_party/WebKit/public/platform/scheduler/base/task_time_observer.h b/third_party/WebKit/public/platform/scheduler/base/task_time_observer.h
index 81714ddd3cd987474b83acb6512f255cff6355e0..a37159609e14808ad6db74ed21130ea62e624db8 100644
--- a/third_party/WebKit/public/platform/scheduler/base/task_time_observer.h
+++ b/third_party/WebKit/public/platform/scheduler/base/task_time_observer.h
@@ -19,13 +19,18 @@ class BLINK_PLATFORM_EXPORT TaskTimeObserver {
   TaskTimeObserver() {}
   virtual ~TaskTimeObserver() {}
 
+  // Callback to be called when task is started.
+  // |task_queue| - TaskQueue on which this task was run,
+  // |start_time| - time in seconds when task started to run,
+  virtual void ReportTaskStartTime(double start_time) {}
+
   // Callback to be called when task is completed.
   // |task_queue| - TaskQueue on which this task was run,
   // |start_time| - time in seconds when task started to run,
   // |end_time| - time in seconds when task was completed.
-  virtual void ReportTaskTime(TaskQueue* task_queue,
-                              double start_time,
-                              double end_time) = 0;
+  virtual void ReportTaskEndTime(TaskQueue* task_queue,
+                                 double start_time,
+                                 double end_time) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TaskTimeObserver);