Hook up RendererMediaSessionManager with browser side

content/renderer/media/android/webmediasession_android.h

Index: content/renderer/media/android/webmediasession_android.h
diff --git a/content/renderer/media/android/webmediasession_android.h b/content/renderer/media/android/webmediasession_android.h
index b27d51a5cee2be13e7b7d54c40ca6e7ea49a9cd1..a71f0de70d3fd6ce6a6f5b9185f9bbb15eb0f195 100644
--- a/content/renderer/media/android/webmediasession_android.h
+++ b/content/renderer/media/android/webmediasession_android.h
@@ -5,6 +5,7 @@
 #ifndef CONTENT_RENDERER_MEDIA_ANDROID_WEBMEDIASESSION_ANDROID_H_
 #define CONTENT_RENDERER_MEDIA_ANDROID_WEBMEDIASESSION_ANDROID_H_
 
+#include "base/id_map.h"
 #include "base/macros.h"
 #include "content/common/content_export.h"
 #include "third_party/WebKit/public/platform/modules/mediasession/WebMediaSession.h"
@@ -21,9 +22,23 @@ class CONTENT_EXPORT WebMediaSessionAndroid : public blink::WebMediaSession {
   void activate(blink::WebMediaSessionActivateCallback*) override;
   void deactivate(blink::WebMediaSessionDeactivateCallback*) override;
 
+  void OnDidActivate(int request_id, bool success);
+  void OnDidDeactivate(int request_id);
+
+  int session_id() const { return session_id_; }
+
  private:
   RendererMediaSessionManager* const session_manager_;
   int session_id_;
+  int next_request_id_;
+
+  using ActivationRequests =
+      IDMap<blink::WebMediaSessionActivateCallback, IDMapOwnPointer>;
+  ActivationRequests activation_requests_;
+
+  using DeactivationRequests =
+      IDMap<blink::WebMediaSessionDeactivateCallback, IDMapOwnPointer>;
+  DeactivationRequests deactivation_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(WebMediaSessionAndroid);
 };