[Media Controls] Add UMA for timeline scrubber

third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011, 2012 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:
  * 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 848 matching lines @@
 }
 
 void MediaControlsImpl::onPlay() {
   updatePlayState();
   m_timeline->setPosition(mediaElement().currentTime());
   updateCurrentTimeDisplay();
 
   startHideMediaControlsTimer();
 }
 
+void MediaControlsImpl::onPlaying() {
+  m_timeline->onPlaying();
+}
+
 void MediaControlsImpl::onPause() {
   updatePlayState();
   m_timeline->setPosition(mediaElement().currentTime());
   updateCurrentTimeDisplay();
   makeOpaque();
 
   stopHideMediaControlsTimer();
 }
 
 void MediaControlsImpl::onTextTracksAddedOrRemoved() {
@@ skipping 236 matching lines @@
   visitor->trace(m_castButton);
   visitor->trace(m_overlayCastButton);
   visitor->trace(m_mediaEventListener);
   visitor->trace(m_windowEventListener);
   visitor->trace(m_orientationLockDelegate);
   MediaControls::trace(visitor);
   HTMLDivElement::trace(visitor);
 }
 
 }  // namespace blink