Adding mojo MediaSessionClient to support media controls

content/browser/media/session/media_session_service_impl.cc

Index: content/browser/media/session/media_session_service_impl.cc
diff --git a/content/browser/media/session/media_session_service_impl.cc b/content/browser/media/session/media_session_service_impl.cc
index c7dbf721bc17a8ad660509ce61968e3bcfe07887..87a0873ea732ffbc39f676a5a5e1edfebf83d35f 100644
--- a/content/browser/media/session/media_session_service_impl.cc
+++ b/content/browser/media/session/media_session_service_impl.cc
@@ -27,6 +27,11 @@ void MediaSessionServiceImpl::Create(
   impl->Bind(std::move(request));
 }
 
+void MediaSessionServiceImpl::SetClient(
+    blink::mojom::MediaSessionClientPtr client) {
+  client_ = std::move(client);
+}
+
 void MediaSessionServiceImpl::SetMetadata(
     const base::Optional<content::MediaMetadata>& metadata) {
   // When receiving a MediaMetadata, the browser process can't trust that it is
@@ -44,6 +49,13 @@ void MediaSessionServiceImpl::SetMetadata(
     MediaSession::Get(contents)->SetMetadata(metadata);
 }
 
+void MediaSessionServiceImpl::DidSetEventHandlerForAction(
+    const std::string& action,
+    bool is_set) {
+  // TODO(zqzhang): Plumb this signal to Java. See https://crbug.com/656563
+  NOTIMPLEMENTED();
+}
+
 void MediaSessionServiceImpl::Bind(
     blink::mojom::MediaSessionServiceRequest request) {
   binding_.reset(new mojo::Binding<blink::mojom::MediaSessionService>(