Utilize PassRefPtr and C++ refs in more places in ShadowRoot code

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 3573 matching lines @@
 
     RefPtr<MediaControls> mediaControls = MediaControls::create(document());
     if (!mediaControls)
         return false;
 
     mediaControls->setMediaController(m_mediaController ? m_mediaController.get() : static_cast<MediaControllerInterface*>(this));
     mediaControls->reset();
     if (isFullscreen())
         mediaControls->enteredFullscreen();
 
-    ensureUserAgentShadowRoot()->appendChild(mediaControls);
+    ensureUserAgentShadowRoot().appendChild(mediaControls);
 
     if (!controls() || !inDocument())
         mediaControls->hide();
 
     return true;
 }
 
 void HTMLMediaElement::configureMediaControls()
 {
     if (!controls() || !inDocument()) {
@@ skipping 263 matching lines @@
 {
     scheduleLayerUpdate();
 }
 
 bool HTMLMediaElement::isInteractiveContent() const
 {
     return fastHasAttribute(controlsAttr);
 }
 
 }