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

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
 
 #include "base/time/time.h"
 #include "public/platform/WebCommon.h"
 
 namespace blink {
 namespace scheduler {
 
 class BLINK_PLATFORM_EXPORT TaskTimeTracker {
  public:
   TaskTimeTracker() {}
   virtual ~TaskTimeTracker() {}
 
+  virtual void ReportTaskStartTime(base::TimeTicks startTime) = 0;
   virtual void ReportTaskTime(base::TimeTicks startTime,
                               base::TimeTicks endTime) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TaskTimeTracker);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_