Implement Audio Focus Manager for desktop.

content/browser/media/session/media_session.h

 // Copyright 2015 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_SESSION_MEDIA_SESSION_H_
 #define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_H_
 
 #include <stddef.h>
 
 #include "base/callback_list.h"
 #include "base/id_map.h"
 #include "base/macros.h"
 #include "content/browser/media/session/media_session_uma_helper.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "content/public/common/media_metadata.h"
 
 class MediaSessionBrowserTest;
 
 namespace content {
 
+class AudioFocusManagerTest;
 class MediaSessionDelegate;
 class MediaSessionObserver;
 class MediaSessionStateObserver;
 class MediaSessionVisibilityBrowserTest;
 
 // MediaSession manages the media session and audio focus for a given
 // WebContents. It is requesting the audio focus, pausing when requested by the
 // system and dropping it on demand.
 // The audio focus can be of two types: Transient or Content. A Transient audio
 // focus will allow other players to duck instead of pausing and will be
@@ skipping 85 matching lines @@
   // this method is introduced temporarily and will be removed later.
   bool IsReallySuspended() const;
 
   // Returns if the session is currently suspended or inactive.
   CONTENT_EXPORT bool IsSuspended() const;
 
  private:
   friend class content::WebContentsUserData<MediaSession>;
   friend class ::MediaSessionBrowserTest;
   friend class content::MediaSessionVisibilityBrowserTest;
+  friend class content::AudioFocusManagerTest;
   friend class content::MediaSessionStateObserver;
 
   CONTENT_EXPORT void SetDelegateForTests(
       std::unique_ptr<MediaSessionDelegate> delegate);
   CONTENT_EXPORT bool IsActiveForTest() const;
   CONTENT_EXPORT Type audio_focus_type_for_test() const;
   CONTENT_EXPORT void RemoveAllPlayersForTest();
   CONTENT_EXPORT MediaSessionUmaHelper* uma_helper_for_test();
 
   enum class State {
@@ skipping 63 matching lines @@
 
   MediaMetadata metadata_;
   base::CallbackList<void(State)> media_session_state_listeners_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaSession);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_H_