[Chromecast] Simplify CastMediaBlocker.

chromecast/browser/cast_media_blocker.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 CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_
 #define CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_
 
 #include "base/macros.h"
 #include "content/public/browser/media_session_observer.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace chromecast {
 namespace shell {
 
 // This class implements a blocking mode for web applications and is used in
 // Chromecast internal code. Media is unblocked by default.
-//
-// TODO(derekjchow): Remove the inheritance from WebContentsObserver.
-// See http://crbug.com/660331
-class CastMediaBlocker : public content::MediaSessionObserver,
-                         content::WebContentsObserver {
+class CastMediaBlocker : public content::MediaSessionObserver {
  public:
-  CastMediaBlocker(content::MediaSession* media_session,
-                   content::WebContents* web_contents);
+  explicit CastMediaBlocker(content::MediaSession* media_session);
   ~CastMediaBlocker() override;
 
   // Sets if the web contents is allowed to play media or not. If media is
   // unblocked, previously suspended elements should begin playing again.
   void BlockMediaLoading(bool blocked);
 
   // content::MediaSessionObserver implementation:
   void MediaSessionStateChanged(bool is_controllable,
                                 bool is_suspended) override;
 
@@ skipping 21 matching lines @@
   bool suspended_;
   bool controllable_;
 
   DISALLOW_COPY_AND_ASSIGN(CastMediaBlocker);
 };
 
 }  // namespace shell
 }  // namespace chromecast
 
 #endif  // CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_