Add a UseCounter for the HTMLMediaElement.canPlayType keySystem argument

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 567 matching lines @@
     setAttribute(srcAttr, url);
 }
 
 HTMLMediaElement::NetworkState HTMLMediaElement::networkState() const
 {
     return m_networkState;
 }
 
 String HTMLMediaElement::canPlayType(const String& mimeType, const String& keySystem) const
 {
+    if (!keySystem.isNull())
+        UseCounter::count(document(), UseCounter::CanPlayTypeKeySystem);
+
     WebMimeRegistry::SupportsType support = supportsType(ContentType(mimeType), keySystem);
     String canPlay;
 
     // 4.8.10.3
     switch (support)
     {
         case WebMimeRegistry::IsNotSupported:
             canPlay = emptyString();
             break;
         case WebMimeRegistry::MayBeSupported:
@@ skipping 3325 matching lines @@
 {
     m_mediaSource->setWebMediaSourceAndOpen(adoptPtr(webMediaSource));
 }
 
 bool HTMLMediaElement::isInteractiveContent() const
 {
     return fastHasAttribute(controlsAttr);
 }
 
 }