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 3c054fcac321c238dc5b61c735d2318c94d4a3f6..aac296b2bceae1c50d344f303b5f85836c1b6833 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"
@@ -84,7 +85,8 @@ void RendererMediaPlayerManager::Initialize(
     const GURL& first_party_for_cookies,
     int demuxer_client_id,
     const GURL& frame_url,
-    bool allow_credentials) {
+    bool allow_credentials,
+    media::WebMediaPlayerDelegate::Observer* observer) {
   MediaPlayerHostMsg_Initialize_Params media_player_params;
   media_player_params.type = type;
   media_player_params.player_id = player_id;
@@ -93,6 +95,8 @@ 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(observer);
 
   Send(new MediaPlayerHostMsg_Initialize(routing_id(), media_player_params));
 }