[Chromecast] Simplify CastMediaBlocker.

chromecast/browser/cast_media_blocker.cc

 // 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.
 
 #include "chromecast/browser/cast_media_blocker.h"
 
 #include "base/threading/thread_checker.h"
 #include "content/public/browser/media_session.h"
 #include "content/public/browser/web_contents.h"
 
 namespace chromecast {
 namespace shell {
 
-CastMediaBlocker::CastMediaBlocker(content::MediaSession* media_session,
-                                   content::WebContents* web_contents)
+CastMediaBlocker::CastMediaBlocker(content::MediaSession* media_session)
     : content::MediaSessionObserver(media_session),
-      content::WebContentsObserver(web_contents),
       blocked_(false),
       paused_by_user_(true),
       suspended_(true),
       controllable_(false) {}
 
 CastMediaBlocker::~CastMediaBlocker() {}
 
 void CastMediaBlocker::BlockMediaLoading(bool blocked) {
   if (blocked_ == blocked)
     return;
@@ skipping 75 matching lines @@
 void CastMediaBlocker::Resume() {
   if (!media_session())
     return;
 
   LOG(INFO) << "Resuming media session.";
   media_session()->Resume(content::MediaSession::SuspendType::SYSTEM);
 }
 
 }  // namespace shell
 }  // namespace chromecast