Remove unnecessary LifecycleObserver::clearContext

third_party/WebKit/Source/modules/vibration/VibrationController.cpp

 /*
  *  Copyright (C) 2012 Samsung Electronics
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 159 matching lines @@
   // |cancel| was in flight, so kick the timer to let |doVibrate| process the
   // pattern.
   m_timerDoVibrate.startOneShot(0, BLINK_FROM_HERE);
 }
 
 void VibrationController::contextDestroyed() {
   cancel();
 
   // If the document context was destroyed, never call the mojo service again.
   m_service.reset();
-
-  // The context is not automatically cleared, so do it manually.
-  ContextLifecycleObserver::clearContext();
-
-  // Page outlives ExecutionContext so stop observing it to avoid having
-  // |pageVisibilityChanged| or |contextDestroyed| called again.
-  PageVisibilityObserver::clearContext();

[haraken, 2016/12/19 06:13:13]

Some objects inherit from both ContextLifecycleObserver and
PageVisibilityObserver. The objects override "contextDestroyed", which is called
when the context is detached and the page is detached. This is really
confusing...

We should introduce contextDestroyed, pageDestroyed, workerThreadDestroyed etc
per lifecycle observer.

 }
 
 void VibrationController::pageVisibilityChanged() {
   if (!page()->isPageVisible())
     cancel();
 }
 
 DEFINE_TRACE(VibrationController) {
   ContextLifecycleObserver::trace(visitor);
   PageVisibilityObserver::trace(visitor);
 }
 
 }  // namespace blink