Implement MediaSession on top of the WebMediaPlayerDelegate.

content/renderer/media/android/renderer_media_player_manager.cc

Index: content/renderer/media/android/renderer_media_player_manager.cc
diff --git a/content/renderer/media/android/renderer_media_player_manager.cc b/content/renderer/media/android/renderer_media_player_manager.cc
index b1b39f223a4a2a56412a78c9352f2f2f30d1ecb3..e2957d94236e3dcb5c78f2632592d52f4fa2090b 100644
--- a/content/renderer/media/android/renderer_media_player_manager.cc
+++ b/content/renderer/media/android/renderer_media_player_manager.cc
@@ -9,6 +9,7 @@
 #include "content/public/common/renderer_preferences.h"
 #include "content/renderer/media/android/webmediaplayer_android.h"
 #include "content/renderer/media/cdm/renderer_cdm_manager.h"
+#include "content/renderer/media/renderer_webmediaplayer_delegate.h"
 #include "content/renderer/render_view_impl.h"
 #include "media/base/cdm_context.h"
 #include "media/base/media_switches.h"
@@ -93,6 +94,9 @@ void RendererMediaPlayerManager::Initialize(
   media_player_params.first_party_for_cookies = first_party_for_cookies;
   media_player_params.frame_url = frame_url;
   media_player_params.allow_credentials = allow_credentials;
+  media_player_params.delegate_id =
+      media::RendererWebMediaPlayerDelegate::GetPlayerId(
+          media_players_[player_id]);
 
   Send(new MediaPlayerHostMsg_Initialize(routing_id(), media_player_params));
 }