Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/html/shadow/MediaControlElements.cpp

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 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.
@@ skipping 16 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/html/shadow/MediaControlElements.h"
 
 #include "RuntimeEnabledFeatures.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
 #include "core/dom/DOMTokenList.h"
 #include "core/dom/FullscreenElementStack.h"
+#include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/MouseEvent.h"
 #include "core/events/ThreadLocalEventNames.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/shadow/MediaControls.h"
 #include "core/html/track/TextTrack.h"
 #include "core/html/track/VTTRegionList.h"
 #include "core/page/EventHandler.h"
 #include "core/frame/Frame.h"
 #include "core/page/Page.h"
 #include "core/page/Settings.h"
@@ skipping 743 matching lines @@
     float fontSize = smallestDimension * 0.05f;
     if (fontSize != m_fontSize) {
         m_fontSize = fontSize;
         setInlineStyleProperty(CSSPropertyFontSize, fontSize, CSSPrimitiveValue::CSS_PX);
     }
 }
 
 // ----------------------------
 
 } // namespace WebCore