Merge/rename two MediaControlElements into their parent classes

Source/core/html/shadow/MediaControls.h

 /*
  * 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 97 matching lines @@
     // Container for the media control elements.
     MediaControlPanelElement* m_panel;
 
     // Container for the text track cues.
     MediaControlTextTrackContainerElement* m_textDisplayContainer;
 
     // Media control elements.
     MediaControlPlayButtonElement* m_playButton;
     MediaControlCurrentTimeDisplayElement* m_currentTimeDisplay;
     MediaControlTimelineElement* m_timeline;
-    MediaControlPanelMuteButtonElement* m_panelMuteButton;
-    MediaControlPanelVolumeSliderElement* m_volumeSlider;
+    MediaControlMuteButtonElement* m_muteButton;
+    MediaControlVolumeSliderElement* m_volumeSlider;
     MediaControlToggleClosedCaptionsButtonElement* m_toggleClosedCaptionsButton;
     MediaControlFullscreenButtonElement* m_fullScreenButton;
     MediaControlTimeRemainingDisplayElement* m_durationDisplay;
     MediaControlPanelEnclosureElement* m_enclosure;
 
     Timer<MediaControls> m_hideFullscreenControlsTimer;
     bool m_isFullscreen;
     bool m_isMouseOverControls;
 };
 
 DEFINE_NODE_TYPE_CASTS(MediaControls, isMediaControls());
 
 }
 
 #endif