Do not use a persistent reference to store srcObject in HTMLMediaElement.

third_party/WebKit/public/platform/WebMediaPlayerSource.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebMediaPlayerSource_h
 #define WebMediaPlayerSource_h
 
 #include "WebCommon.h"
 #include "WebMediaStream.h"
 #include "WebURL.h"
 
 namespace blink {
 
 class BLINK_PLATFORM_EXPORT WebMediaPlayerSource {
 public:
     WebMediaPlayerSource();
     explicit WebMediaPlayerSource(const WebURL&);
     explicit WebMediaPlayerSource(const WebMediaStream&);
     ~WebMediaPlayerSource();
 
     bool isURL() const;
     WebURL getAsURL() const;
 
-    bool isMediaProviderObject() const;
-
     bool isMediaStream() const;
     WebMediaStream getAsMediaStream() const;
 
 private:
     WebURL m_url;
     WebMediaStream m_mediaStream;
 };
 
 } // namespace blink
 
 #endif // WebMediaPlayerSource_h