Move audio focus control from media/ to content/ and make it per WebContents.

content/browser/media/android/browser_media_player_manager.cc

Index: content/browser/media/android/browser_media_player_manager.cc
diff --git a/content/browser/media/android/browser_media_player_manager.cc b/content/browser/media/android/browser_media_player_manager.cc
index 68268f7406d215d98953787c36061d5b870c0f8f..111602c571dadc68a1f9490fcb2fd414fffab8e9 100644
--- a/content/browser/media/android/browser_media_player_manager.cc
+++ b/content/browser/media/android/browser_media_player_manager.cc
@@ -10,6 +10,7 @@
 #include "content/browser/android/media_players_observer.h"
 #include "content/browser/media/android/browser_demuxer_android.h"
 #include "content/browser/media/android/media_resource_getter_impl.h"
+#include "content/browser/media/android/media_session.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_contents_view_android.h"
 #include "content/common/media/media_player_messages_android.h"
@@ -160,6 +161,7 @@ BrowserMediaPlayerManager::~BrowserMediaPlayerManager() {
   for (MediaPlayerAndroid* player : players_)
     player->DeleteOnCorrectThread();
 
+  MediaSession::Get(web_contents())->AbandonAudioFocus(this);

[whywhat, 2015/05/12 12:50:44]

nit: s/Get/From?

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

I used ::Get() instead of ::From() because ::FromWebContents() is used to return
a WebContentsUserData but wouldn't create it by default. ::Get() will create the
instance if needed, like a singleton pattern.

   players_.weak_clear();
 }
 
@@ -228,6 +230,8 @@ void BrowserMediaPlayerManager::OnMediaMetadataChanged(
 
 void BrowserMediaPlayerManager::OnPlaybackComplete(int player_id) {
   Send(new MediaPlayerMsg_MediaPlaybackCompleted(RoutingID(), player_id));
+  MediaSession::Get(web_contents())->AbandonAudioFocus(this, player_id);
+
   if (fullscreen_player_id_ == player_id)
     video_view_->OnPlaybackComplete();
 }
@@ -341,6 +345,20 @@ void BrowserMediaPlayerManager::RequestFullScreen(int player_id) {
   Send(new MediaPlayerMsg_RequestFullscreen(RoutingID(), player_id));
 }
 
+bool BrowserMediaPlayerManager::RequestPlay(int player_id) {
+  MediaPlayerAndroid* player = GetPlayer(player_id);

[whywhat, 2015/05/12 12:50:45]

I believe this should return true for remote players or remote players shouldn't
call this method.

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

Remote players do not call this method AFAICT. However, they grab audiofocus in
their own way from the lockscreen code.

+  DCHECK(player);
+  MediaSession::Type media_session_type =
+      player->GetDuration().InSeconds() > 5 ? MediaSession::Type::Content

[whywhat, 2015/05/12 12:50:45]

5 is a magic constant! make it a named one, please.

[qinmin, 2015/05/15 18:06:19]

You need to special treat duration==0 case. Duration is not available for HLS or
if wifi is not available. 

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

Oups again.
It seems that we don't get duration==0 for HLS. Also, ::RequestPlay() is called
when the data is loaded and ready to be played so if the wifi isn't available,
this will not be called. Could that be the reason why duration!=0 for HLS?

[qinmin, 2015/05/20 21:35:24]

HLS duration is never trustworthy on android. If wifi isn't available, this will
also be called if the device is on mobile networks. But since startInternal is
always called after prepare(), so the player should have the duration here.

[mlamouri (slow - plz ping), 2015/05/22 15:58:52]

Yeah, we made the call in StartInternal() on purpose so we don't cut other audio
if the player ends up not playable.

My understanding is that there is nothing to change here, let me know if I'm
misunderstanding.

+                                            : MediaSession::Type::Transient;
+
+  bool succeeded = MediaSession::Get(web_contents())->RequestAudioFocus(
+      this, player_id, media_session_type);
+  if (!succeeded)
+    OnSuspend(player_id);
+  return succeeded;
+}
+
 #if defined(VIDEO_HOLE)
 void BrowserMediaPlayerManager::AttachExternalVideoSurface(int player_id,
                                                            jobject surface) {
@@ -365,6 +383,22 @@ void BrowserMediaPlayerManager::OnFrameInfoUpdated() {
     external_video_surface_container_->OnFrameInfoUpdated();
 }
 
+void BrowserMediaPlayerManager::OnSuspend(int player_id) {
+  MediaPlayerAndroid* player = GetPlayer(player_id);
+  DCHECK(player);
+
+  player->Pause(true);
+  Send(new MediaPlayerMsg_DidMediaPlayerPause(RoutingID(), player_id));
+}
+
+void BrowserMediaPlayerManager::OnResume(int player_id) {
+  MediaPlayerAndroid* player = GetPlayer(player_id);
+  DCHECK(player);
+
+  player->Start();
+  Send(new MediaPlayerMsg_DidMediaPlayerPlay(RoutingID(), player_id));
+}
+
 void BrowserMediaPlayerManager::OnNotifyExternalSurface(
     int player_id, bool is_request, const gfx::RectF& rect) {
   if (!web_contents_)
@@ -503,6 +537,8 @@ void BrowserMediaPlayerManager::OnPause(
   MediaPlayerAndroid* player = GetPlayer(player_id);
   if (player)
     player->Pause(is_media_related_action);
+
+  MediaSession::Get(web_contents())->AbandonAudioFocus(this, player_id);
 }
 
 void BrowserMediaPlayerManager::OnSetVolume(int player_id, double volume) {