Make DocumentLoader::timing return a reference

Source/core/animation/AnimationTimeline.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 166 matching lines @@
 
 void AnimationTimeline::AnimationTimelineTiming::trace(Visitor* visitor)
 {
     visitor->trace(m_timeline);
     AnimationTimeline::PlatformTiming::trace(visitor);
 }
 
 double AnimationTimeline::zeroTime()
 {
     if (!m_zeroTimeInitialized && m_document && m_document->loader()) {
-        m_zeroTime = m_document->loader()->timing()->referenceMonotonicTime();
+        m_zeroTime = m_document->loader()->timing().referenceMonotonicTime();
         m_zeroTimeInitialized = true;
     }
     return m_zeroTime;
 }
 
 double AnimationTimeline::currentTime(bool& isNull)
 {
     return currentTimeInternal(isNull) * 1000;
 }
 
@@ skipping 114 matching lines @@
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_document);
     visitor->trace(m_timing);
     visitor->trace(m_playersNeedingUpdate);
     visitor->trace(m_players);
 #endif
 }
 
 } // namespace