Make WebTaskRunner ThreadSafeRefCounted

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

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 163 matching lines @@
   if (!executionContext)
     return;
 
   executionContext->timers()->setTimerNestingLevel(0);
   // Eagerly unregister as ExecutionContext observer.
   clearContext();
   // Eagerly clear out |action|'s resources.
   action->dispose();
 }
 
-WebTaskRunner* DOMTimer::timerTaskRunner() const {
+RefPtr<WebTaskRunner> DOMTimer::timerTaskRunner() const {
   return getExecutionContext()->timers()->timerTaskRunner();
 }
 
 DEFINE_TRACE(DOMTimer) {
   visitor->trace(m_action);
   SuspendableTimer::trace(visitor);
 }
 
 }  // namespace blink