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;
 
   // Called by WebContentsImpl when the audible state may have changed.
   void MaybeUpdateAudibleState();
 
   // WebContentsObserver implementation.
   void WebContentsDestroyed() override;
   void RenderFrameDeleted(RenderFrameHost* render_frame_host) override;
   bool OnMessageReceived(const IPC::Message& message,
                          RenderFrameHost* render_frame_host) override;
   void WasShown() override;
   void WasHidden() override;
 
+#if defined(OS_ANDROID)

[DaleCurtis, 2016/02/17 20:16:54]

Can you keep this on MWCOA? I'd like to avoid reintroducing any #ifdefs to this
class. Perhaps by exposing a protected method that derived classes can use to
access the session map?

[mlamouri (slow - plz ping), 2016/02/23 20:27:55]

Done.

+  // Initiates a synchronous MediaSession request for browser side players.
+  //
+  // TODO(dalecurtis): Delete this method once we're no longer using WMPA and
+  // the BrowserMediaPlayerManagers.  Tracked by http://crbug.com/580626
+  bool RequestPlay(RenderFrameHost* render_frame_host,
+                   int delegate_id,
+                   bool has_audio,
+                   bool is_remote,
+                   base::TimeDelta duration);
+#endif // OS_ANDROID
+
   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_;
   }
 
  private:
   void OnMediaDestroyed(RenderFrameHost* render_frame_host, int delegate_id);
@@ skipping 32 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_