Let CastMediaBlocker observe MediaSession instead of WebContents [FOR TRY]

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 "base/callback_forward.h"
-#include "content/public/browser/web_contents_observer.h"
-
-namespace content {
-class WebContents;
-}  // namespace content
+#include "content/public/browser/media_session_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.
-class CastMediaBlocker : public content::WebContentsObserver {
+class CastMediaBlocker : public content::MediaSessionObserver {
  public:
-  explicit CastMediaBlocker(content::WebContents* web_contents);
-
-  // Constructor for test. |suspend_cb| and |resume_cb| will be called when
-  // Suspend() and Resume() are called.
-  CastMediaBlocker(content::WebContents* web_contents,
-                   const base::Closure& suspend_cb,
-                   const base::Closure& resume_cb);
-
+  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::WebContentsObserver implementation:
+  // content::MediaSessionObserver implementation:
   void MediaSessionStateChanged(bool is_controllable,
                                 bool is_suspended) override;
 
  protected:
   bool media_loading_blocked() const { return blocked_; }
 
   // Blocks or unblocks the render process from loading new media
   // according to |media_loading_blocked_|.
   virtual void UpdateMediaBlockedState() {}
 
  private:
   // Suspends or resumes the media session for the web contents.
   void Suspend();
   void Resume();
 
-  base::Closure suspend_cb_;
-  base::Closure resume_cb_;
-
   // Whether or not media should be blocked. This value cache's the last call to
   // BlockMediaLoading. Is false by default.
   bool blocked_;
 
   // Whether or not the user paused media on the page.
   bool paused_by_user_;
 
   // Whether or not media in the app can be controlled and if media is currently
   // suspended. These variables cache arguments from MediaSessionStateChanged().
   bool suspended_;
   bool controllable_;
 
   DISALLOW_COPY_AND_ASSIGN(CastMediaBlocker);
 };
 
 }  // namespace shell
 }  // namespace chromecast
 
 #endif  // CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_