NOT FOR LANDING Implement WebMediaSession

content/browser/media/android/media_session.cc

 // 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.
 
 #include "content/browser/media/android/media_session.h"
 
 #include "base/android/jni_android.h"
 #include "content/browser/media/android/media_session_observer.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 37 matching lines @@
     session->Initialize();
   }
   return session;
 }
 
 MediaSession::~MediaSession() {
   DCHECK(players_.empty());
   DCHECK(audio_focus_state_ == State::INACTIVE);
 }
 
+bool MediaSession::Activate() {
+  if (audio_focus_state_ == State::ACTIVE)
+    return true;
+
+  const Type type = Type::Content;
+  if (!RequestSystemAudioFocus(type))
+    return false;
+
+  audio_focus_state_ = State::ACTIVE;
+  audio_focus_type_ = type;
+  UpdateWebContents();
+
+  return true;
+}
+
+void MediaSession::Deactivate() {
+  AbandonSystemAudioFocusIfNeeded();

[mlamouri (slow - plz ping), 2015/08/24 12:55:24]

Looking at that code, it's a bit odd that RequestSystemAudioFocus() doesn't
update audio_focus_state and doesn't call UpdateWebContents() but
AbandonSystemAudioFocusIfNeeded() does.

[philipj_slow, 2015/08/26 07:39:48]

Yes, this doesn't make any sense, I just hacked until it was possible to get a
notification showing using the API. If we split the responsibility for
monitoring media players out of this class, then I think we would end up with a
much cleaner Activate() and Deactivate(), that would be the only places to
request or abandon audio focus.

+  DCHECK(audio_focus_state_ == State::INACTIVE);
+}
+
 bool MediaSession::AddPlayer(MediaSessionObserver* observer,
                              int player_id,
                              Type type) {
   // If the audio focus is already granted and is of type Content, there is
   // nothing to do. If it is granted of type Transient the requested type is
   // also transient, there is also nothing to do. Otherwise, the session needs
   // to request audio focus again.
   if (audio_focus_state_ == State::ACTIVE &&
       (audio_focus_type_ == Type::Content || audio_focus_type_ == type)) {
     players_.insert(PlayerIdentifier(observer, player_id));
@@ skipping 161 matching lines @@
 
   audio_focus_state_ = State::INACTIVE;
   UpdateWebContents();
 }
 
 void MediaSession::UpdateWebContents() {
   static_cast<WebContentsImpl*>(web_contents())->OnMediaSessionStateChanged();
 }
 
 }  // namespace content