Make MediaSession a runtime-enabled feature on Desktop.

content/browser/media/android/media_session_controller.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 CONTENT_BROWSER_MEDIA_ANDROID_MEDIA_SESSION_CONTROLLER_H_
-#define CONTENT_BROWSER_MEDIA_ANDROID_MEDIA_SESSION_CONTROLLER_H_
-
-#include "base/time/time.h"
-#include "content/browser/media/android/media_session_observer.h"
-#include "content/common/content_export.h"
-#include "content/public/browser/web_contents_observer.h"
-
-namespace content {
-
-class MediaSession;
-class MediaWebContentsObserver;
-
-// Helper class for controlling a single player's MediaSession instance.  Sends
-// browser side MediaSession commands back to a player hosted in the renderer
-// process.
-class CONTENT_EXPORT MediaSessionController : public MediaSessionObserver {
- public:
-  MediaSessionController(const WebContentsObserver::MediaPlayerId& id,
-                         MediaWebContentsObserver* media_web_contents_observer);
-  ~MediaSessionController() override;
-
-  // Minimum duration of content for a MediaSession instance to be created.
-  enum { kMinimumDurationForContentSecs = 5 };
-
-  // Clients must call this after construction and destroy the controller if it
-  // returns false.  May be called more than once; does nothing if none of the
-  // input parameters have changed since the last call.
-  //
-  // Note: Once a session has been initialized with |has_audio| as true, all
-  // future calls to Initialize() will retain this flag.
-  // TODO(dalecurtis): Delete sticky audio once we're no longer using WMPA and
-  // the BrowserMediaPlayerManagers.  Tracked by http://crbug.com/580626
-  bool Initialize(bool has_audio, bool is_remote, base::TimeDelta duration);
-
-  // Must be called when a pause occurs on the renderer side media player; keeps
-  // the MediaSession instance in sync with renderer side behavior.
-  void OnPlaybackPaused();
-
-  // MediaSessionObserver implementation.
-  void OnSuspend(int player_id) override;
-  void OnResume(int player_id) override;
-  void OnSetVolumeMultiplier(int player_id, double volume_multiplier) override;
-
-  // Test helpers.
-  int get_player_id_for_testing() const { return player_id_; }
-
- private:
-  const WebContentsObserver::MediaPlayerId id_;
-
-  // Non-owned pointer; |media_web_contents_observer_| is the owner of |this|.
-  MediaWebContentsObserver* const media_web_contents_observer_;
-
-  // Non-owned pointer; lifetime is the same as |media_web_contents_observer_|.
-  MediaSession* const media_session_;
-
-  int player_id_ = 0;
-  bool has_session_ = false;
-
-  DISALLOW_COPY_AND_ASSIGN(MediaSessionController);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_MEDIA_ANDROID_MEDIA_SESSION_CONTROLLER_H_