[MediaRouter] Update MR-2-Extension's PostMessage to return boolean.

chrome/browser/media/router/media_router_mojo_impl.cc

Index: chrome/browser/media/router/media_router_mojo_impl.cc
diff --git a/chrome/browser/media/router/media_router_mojo_impl.cc b/chrome/browser/media/router/media_router_mojo_impl.cc
index c65700d7299ee86a1b69def1d91ac76144301318..e9bfc31ab262658db9b25ef8c2f4e37b49eaccfe 100644
--- a/chrome/browser/media/router/media_router_mojo_impl.cc
+++ b/chrome/browser/media/router/media_router_mojo_impl.cc
@@ -175,11 +175,12 @@ void MediaRouterMojoImpl::CloseRoute(const MediaRoute::Id& route_id) {
 }
 
 void MediaRouterMojoImpl::PostMessage(const MediaRoute::Id& route_id,
-                                      const std::string& message) {
+                                      const std::string& message,
+                                      const PostMessageCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   RunOrDefer(base::Bind(&MediaRouterMojoImpl::DoPostMessage,
-                        base::Unretained(this), route_id, message));
+                        base::Unretained(this), route_id, message, callback));
 }
 
 void MediaRouterMojoImpl::ClearIssue(const Issue::Id& issue_id) {
@@ -282,9 +283,10 @@ void MediaRouterMojoImpl::DoCloseRoute(const MediaRoute::Id& route_id) {
 }
 
 void MediaRouterMojoImpl::DoPostMessage(const MediaRoute::Id& route_id,
-                                        const std::string& message) {
+                                        const std::string& message,
+                                        const PostMessageCallback& callback) {
   DVLOG_WITH_INSTANCE(1) << "PostMessage " << route_id;
-  mojo_media_router_->PostMessage(route_id, message);
+  mojo_media_router_->PostMessage(route_id, message, callback);
 }
 
 void MediaRouterMojoImpl::DoClearIssue(const Issue::Id& issue_id) {