Do the codec string parsing for MSE in media, instead of Blink

Source/platform/ContentType.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2009 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 20 matching lines @@
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT ContentType {
 public:
     explicit ContentType(const String& type);
 
     String parameter(const String& parameterName) const;
     String type() const;
-    Vector<String> codecs() const;
     const String& raw() const { return m_type; }
 private:
     String m_type;
 };
 
 } // namespace blink
 
 #endif // ContentType_h