Makes SetFocus() notify callback correctly on failure

components/mus/ws/display.h

 // 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.
 
 #ifndef COMPONENTS_MUS_WS_DISPLAY_H_
 #define COMPONENTS_MUS_WS_DISPLAY_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 97 matching lines @@
     return const_cast<WindowManagerState*>(
         const_cast<const Display*>(this)->GetActiveWindowManagerState());
   }
   const WindowManagerState* GetActiveWindowManagerState() const;
   size_t num_window_manger_states() const {
     return window_manager_state_map_.size();
   }
 
   // TODO(sky): this should only be called by WindowServer, move to interface
   // used by WindowServer.
-  void SetFocusedWindow(ServerWindow* window);
+  // See description of WindowServer::SetFocusedWindow() for details on return
+  // value.
+  bool SetFocusedWindow(ServerWindow* window);
   // NOTE: this returns the focused window only if the focused window is in this
   // display. If this returns null focus may be in another display.
   ServerWindow* GetFocusedWindow();
 
   void ActivateNextWindow();
 
   void AddActivationParent(ServerWindow* window);
   void RemoveActivationParent(ServerWindow* window);
 
   void UpdateTextInputState(ServerWindow* window,
@@ skipping 89 matching lines @@
 
   cc::SurfaceId top_level_surface_id_;
 
   DISALLOW_COPY_AND_ASSIGN(Display);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_DISPLAY_H_