Avoid double lookup of crossorigin attribute.

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 3907 matching lines @@
 void HTMLMediaElement::applyMediaFragmentURI()
 {
     if (m_fragmentStartTime != MediaPlayer::invalidTime()) {
         m_sentEndEvent = false;
         seek(m_fragmentStartTime, IGNORE_EXCEPTION);
     }
 }
 
 MediaPlayerClient::CORSMode HTMLMediaElement::mediaPlayerCORSMode() const
 {
-    if (!fastHasAttribute(crossoriginAttr))
+    const AtomicString& crossOriginMode = fastGetAttribute(crossoriginAttr);
+    if (crossOriginMode.isNull())
         return Unspecified;
-    if (equalIgnoringCase(fastGetAttribute(crossoriginAttr), "use-credentials"))
+    if (equalIgnoringCase(crossOriginMode, "use-credentials"))
         return UseCredentials;
     return Anonymous;
 }
 
 void HTMLMediaElement::removeBehaviorsRestrictionsAfterFirstUserGesture()
 {
     m_restrictions = NoRestrictions;
 }
 
 void HTMLMediaElement::mediaPlayerSetWebLayer(blink::WebLayer* webLayer)
@@ skipping 25 matching lines @@
 {
     m_mediaSource->setWebMediaSourceAndOpen(adoptPtr(webMediaSource));
 }
 
 bool HTMLMediaElement::isInteractiveContent() const
 {
     return fastHasAttribute(controlsAttr);
 }
 
 }