Make MediaSession a runtime-enabled feature on Desktop.

content/browser/media/media_web_contents_observer.h

 // Copyright 2014 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 CONTENT_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_
 #define CONTENT_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <set>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "content/browser/media/session/media_session_controllers_manager.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace content {
+
 class PowerSaveBlocker;
 
 // This class manages all RenderFrame based media related managers at the
 // browser side. It receives IPC messages from media RenderFrameObservers and
 // forwards them to the corresponding managers. The managers are responsible
 // for sending IPCs back to the RenderFrameObservers at the render side.
 class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
  public:
   explicit MediaWebContentsObserver(WebContents* web_contents);
   ~MediaWebContentsObserver() override;
@@ skipping 10 matching lines @@
   void WasHidden() override;
 
   bool has_audio_power_save_blocker_for_testing() const {
     return !!audio_power_save_blocker_;
   }
 
   bool has_video_power_save_blocker_for_testing() const {
     return !!video_power_save_blocker_;
   }
 
+ protected:
+  MediaSessionControllersManager& session_controllers_manager() {

[DaleCurtis, 2016/02/26 03:22:50]

non-const& aren't allowed by the style guide.

[mlamouri (slow - plz ping), 2016/02/26 12:26:17]

Done.

+    return session_controllers_manager_;
+  }
+
  private:
   void OnMediaDestroyed(RenderFrameHost* render_frame_host, int delegate_id);
   void OnMediaPaused(RenderFrameHost* render_frame_host,
                      int delegate_id,
                      bool reached_end_of_stream);
   void OnMediaPlaying(RenderFrameHost* render_frame_host,
                       int delegate_id,
                       bool has_video,
                       bool has_audio,
                       bool is_remote,
@@ skipping 24 matching lines @@
   void RemoveAllMediaPlayerEntries(RenderFrameHost* render_frame_host,
                                    ActiveMediaPlayerMap* player_map,
                                    std::set<MediaPlayerId>* removed_players);
 
   // Tracking variables and associated power save blockers for media playback.
   ActiveMediaPlayerMap active_audio_players_;
   ActiveMediaPlayerMap active_video_players_;
   scoped_ptr<PowerSaveBlocker> audio_power_save_blocker_;
   scoped_ptr<PowerSaveBlocker> video_power_save_blocker_;
 
+  MediaSessionControllersManager session_controllers_manager_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaWebContentsObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_