Let CastMediaBlocker observe MediaSession instead of WebContents

chromecast/browser/cast_media_blocker.h

Index: chromecast/browser/cast_media_blocker.h
diff --git a/chromecast/browser/cast_media_blocker.h b/chromecast/browser/cast_media_blocker.h
index b3350603f7b1fb448130768b7a7eb26cca37b899..d44ec6e04e96bb78aeea2af1be04e3b8a155dbe8 100644
--- a/chromecast/browser/cast_media_blocker.h
+++ b/chromecast/browser/cast_media_blocker.h
@@ -6,35 +6,29 @@
 #define CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_
 
 #include "base/macros.h"
-#include "base/callback_forward.h"
+#include "content/public/browser/media_session_observer.h"
 #include "content/public/browser/web_contents_observer.h"
 
-namespace content {
-class WebContents;
-}  // namespace content
-
 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 {
+//
+// TODO(derekjchow): Remove the inheritance from WebContentsObserver.
+// See http://crbug.com/660331
+class CastMediaBlocker : public content::MediaSessionObserver,
+                         content::WebContentsObserver {

[halliwell, 2016/10/28 17:33:29]

This inheritance seems pointless now.  Derek, are you planning to handle the
TODO here more or less immediately?

[derekjchow1, 2016/10/28 17:35:41]

Yes, I requested this so I could synchronize changing our internal builds with
the public one.

  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,
+                            content::WebContents* web_contents);

[halliwell, 2016/10/28 17:33:29]

nit: remove explicit

   ~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;
 
@@ -50,9 +44,6 @@ class CastMediaBlocker : public content::WebContentsObserver {
   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_;