Revert of Move throttling of background timers into the renderer scheduler

third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 131 matching lines @@
     // (see DOMTimer comment for more.)
     EAGERLY_FINALIZE();
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         visitor->trace(m_event);
         visitor->trace(m_window);
         visitor->trace(m_stackTrace);
         SuspendableTimer::trace(visitor);
     }
 
-    // TODO(alexclarke): Override timerTaskRunner() to pass in a document specific default task runner.
+    WebTaskRunner* timerTaskRunner() override
+    {
+        return m_window->document()->timerTaskRunner();
+    }
 
 private:
     void fired() override
     {
         InspectorInstrumentationCookie cookie = InspectorInstrumentation::traceAsyncOperationCompletedCallbackStarting(executionContext(), m_asyncOperationId);
         // Prevent calls to stop triggered from the event handler to
         // kill this object.
         m_preventDestruction = true;
         m_window->postMessageTimerFired(this);
         // Will destroy this object
@@ skipping 1365 matching lines @@
 {
     // If the LocalDOMWindow still has a frame reference, that frame must point
     // back to this LocalDOMWindow: otherwise, it's easy to get into a situation
     // where script execution leaks between different LocalDOMWindows.
     if (m_frameObserver->frame())
         ASSERT_WITH_SECURITY_IMPLICATION(m_frameObserver->frame()->domWindow() == this);
     return m_frameObserver->frame();
 }
 
 } // namespace blink