[MediaSession, Android] Adding visibility tests for MediaSession

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 MediaSessionDelegate;
 class MediaSessionObserver;
+class MediaSessionStateObserver;
+class MediaSessionVisibilityBrowserTestBase;
 
 // 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
 // declared as temporary to the system. A Content audio focus will not be
 // declared as temporary and will not allow other players to duck. If a given
 // WebContents can only have one audio focus at a time, it will be Content in
 // case of Transient and Content audio focus are both requested.
@@ skipping 82 matching lines @@
   // change all the callers and make the current refactoring ridiculously huge,
   // 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::MediaSessionVisibilityBrowserTestBase;
+  friend class content::MediaSessionStateObserver;
 
   CONTENT_EXPORT void SetDelegateForTests(
       scoped_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 {
     ACTIVE,
@@ skipping 11 matching lines @@
 
     // Hash operator for base::hash_map<>.
     struct Hash {
       size_t operator()(const PlayerIdentifier& player_identifier) const;
     };
 
     MediaSessionObserver* observer;
     int player_id;
   };
   using PlayersMap = base::hash_set<PlayerIdentifier, PlayerIdentifier::Hash>;
+  typedef base::Callback<void(State)> StateChangedCallback;

[DaleCurtis, 2016/03/31 16:50:26]

as of c++11 we use 'using' now, check out http://chromium-cpp.appspot.com

[Zhiqiang Zhang (Slow), 2016/03/31 19:58:39]

Done.

 
   CONTENT_EXPORT explicit MediaSession(WebContents* web_contents);
 
   void Initialize();
 
   CONTENT_EXPORT void OnSuspendInternal(SuspendType type, State new_state);
   CONTENT_EXPORT void OnResumeInternal(SuspendType type);
 
   // Requests audio focus to the MediaSessionDelegate.
   // Returns whether the request was granted.
   bool RequestSystemAudioFocus(Type type);
 
   // To be called after a call to AbandonAudioFocus() in order request the
   // delegate to abandon the audio focus.
   void AbandonSystemAudioFocusIfNeeded();
 
   // Notifies WebContents about the state change of the media session.
   void UpdateWebContents();
 
   // Internal method that should be used instead of setting audio_focus_state_.
   // It sets audio_focus_state_ and notifies observers about the state change.
   void SetAudioFocusState(State audio_focus_state);
 
+  // Registers a MediaSession state change callback.
+  CONTENT_EXPORT scoped_ptr<base::CallbackList<void(State)>::Subscription>
+  RegisterMediaSessionStateChangedCallbackForTest(
+      const StateChangedCallback& cb);
+
   scoped_ptr<MediaSessionDelegate> delegate_;
   PlayersMap players_;
 
   State audio_focus_state_;
   SuspendType suspend_type_;
   Type audio_focus_type_;
 
   MediaSessionUmaHelper uma_helper_;
 
   // The volume multiplier of this session. All players in this session should
   // multiply their volume with this multiplier to get the effective volume.
   double volume_multiplier_;
 
   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_