Hook up RendererMediaSessionManager with browser side

content/renderer/media/android/webmediasession_android.cc

Index: content/renderer/media/android/webmediasession_android.cc
diff --git a/content/renderer/media/android/webmediasession_android.cc b/content/renderer/media/android/webmediasession_android.cc
index 7eddd31333dd2a71f9a002139f0a9ab1c2a00500..b10d5f260b9470e101a3bf377d842ace50a92e12 100644
--- a/content/renderer/media/android/webmediasession_android.cc
+++ b/content/renderer/media/android/webmediasession_android.cc
@@ -22,19 +22,13 @@ WebMediaSessionAndroid::~WebMediaSessionAndroid() {
 }
 
 void WebMediaSessionAndroid::activate(
-    blink::WebMediaSessionActivateCallback* raw_callback) {
-  NOTIMPLEMENTED();
-
-  scoped_ptr<blink::WebMediaSessionActivateCallback> callback(raw_callback);
-  callback->onError(blink::WebMediaSessionError::Activate);
+    blink::WebMediaSessionActivateCallback* callback) {
+  session_manager_->Activate(session_id_, make_scoped_ptr(callback));
 }
 
 void WebMediaSessionAndroid::deactivate(
-    blink::WebMediaSessionDeactivateCallback* raw_callback) {
-  NOTIMPLEMENTED();
-
-  scoped_ptr<blink::WebMediaSessionDeactivateCallback> callback(raw_callback);
-  callback->onSuccess();
+    blink::WebMediaSessionDeactivateCallback* callback) {
+  session_manager_->Deactivate(session_id_, make_scoped_ptr(callback));
 }
 
 void WebMediaSessionAndroid::setMetadata(