mus: Notify the client whether adding an accelerator was successful.

components/mus/ws/window_tree_host_impl.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/mus/ws/window_tree_host_impl.h"
 
 #include "base/debug/debugger.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/mus/common/types.h"
 #include "components/mus/ws/connection_manager.h"
@@ skipping 121 matching lines @@
 }
 
 void WindowTreeHostImpl::SetSize(mojo::SizePtr size) {
   display_manager_->SetViewportSize(size.To<gfx::Size>());
 }
 
 void WindowTreeHostImpl::SetTitle(const mojo::String& title) {
   display_manager_->SetTitle(title.To<base::string16>());
 }
 
-void WindowTreeHostImpl::AddAccelerator(uint32_t id,
-                                        mojom::EventMatcherPtr event_matcher) {
-  event_dispatcher_.AddAccelerator(id, event_matcher.Pass());
+void WindowTreeHostImpl::AddAccelerator(
+    uint32_t id,
+    mojom::EventMatcherPtr event_matcher,
+    const AddAcceleratorCallback& callback) {
+  bool success = event_dispatcher_.AddAccelerator(id, event_matcher.Pass());
+  callback.Run(success);
 }
 
 void WindowTreeHostImpl::RemoveAccelerator(uint32_t id) {
   event_dispatcher_.RemoveAccelerator(id);
 }
 
 void WindowTreeHostImpl::AddActivationParent(uint32_t window_id) {
   ServerWindow* window =
       connection_manager_->GetWindow(WindowIdFromTransportId(window_id));
   if (window)
@@ skipping 227 matching lines @@
                          &WindowTreeHostImpl::OnEventAckTimeout);
 }
 
 void WindowTreeHostImpl::OnWindowDestroyed(ServerWindow* window) {
   windows_needing_frame_destruction_.erase(window);
   window->RemoveObserver(this);
 }
 
 }  // namespace ws
 }  // namespace mus