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

media/base/android/media_source_player.cc

Index: media/base/android/media_source_player.cc
diff --git a/media/base/android/media_source_player.cc b/media/base/android/media_source_player.cc
index ca130892b55bce020479d245d27a59ca29177035..5f6eb96f874ddf8c6752fe17ac693157818d1299 100644
--- a/media/base/android/media_source_player.cc
+++ b/media/base/android/media_source_player.cc
@@ -218,6 +218,9 @@ void MediaSourcePlayer::StartInternal() {
   if (pending_event_ != NO_EVENT_PENDING)
     return;
 
+  if (!manager()->RequestPlay(player_id()))
+    return;
+
   // When we start, we could have new demuxed data coming in. This new data
   // could be clear (not encrypted) or encrypted with different keys. So key
   // related info should all be cleared.