[Android] Added a runtime flag to enable autoplay of muted videos.

third_party/WebKit/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 3655 matching lines @@
     return m_lockedPendingUserGesture;
 }
 
 void HTMLMediaElement::unlockUserGesture()
 {
     m_lockedPendingUserGesture = false;
 }
 
 bool HTMLMediaElement::isGestureNeededForPlayback() const
 {
-    return m_lockedPendingUserGesture
-        && !m_autoplayHelper->isGestureRequirementOverridden();
+    if (!m_lockedPendingUserGesture)
+        return false;
+
+    if (muted() && RuntimeEnabledFeatures::autoplayMutedVideosEnabled())
+        return false;
+
+    if (m_autoplayHelper->isGestureRequirementOverridden())
+        return false;
+
+    return true;
 }
 
 void HTMLMediaElement::setNetworkState(NetworkState state)
 {
     if (m_networkState != state) {
         m_networkState = state;
         if (MediaControls* controls = mediaControls())
             controls->networkStateChanged();
     }
 }
@@ skipping 230 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect() const
 {
     IntRect result;
     if (LayoutObject* object = m_element->layoutObject())
         result = object->absoluteBoundingBoxRect();
     return result;
 }
 
 } // namespace blink