Include viewport visibility checks for autoplay experiment.

Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 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 3726 matching lines @@
 void HTMLMediaElement::removeUserGestureRequirement()
 {
     m_userGestureRequiredForPlay = false;
 }
 
 void HTMLMediaElement::setInitialPlayWithoutUserGestures(bool value)
 {
     m_initialPlayWithoutUserGesture = value;
 }
 
+void HTMLMediaElement::notifyPositionMayHaveChanged()
+{
+    m_autoplayHelper.positionChanged();
+}
+
+void HTMLMediaElement::triggerAutoplayViewportCheck()
+{
+    m_autoplayHelper.triggerAutoplayViewportCheck();
+}
+
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!Heap::isHeapObjectAlive(m_audioSourceNode))
         audioSourceProvider().setClient(nullptr);
 }
 
 void HTMLMediaElement::AudioSourceProviderImpl::wrap(WebAudioSourceProvider* provider)
 {
     MutexLocker locker(provideInputLock);
@@ skipping 49 matching lines @@
     visitor->trace(m_client);
 }
 
 DEFINE_TRACE(HTMLMediaElement::AudioSourceProviderImpl)
 {
     visitor->trace(m_client);
 }
 #endif
 
 }