Makes SetFocus() notify callback correctly on failure

components/mus/ws/display.h

Index: components/mus/ws/display.h
diff --git a/components/mus/ws/display.h b/components/mus/ws/display.h
index b83c11d917229b154a98bbbca179afd51f171c48..ba7cebf5841d867ff8e18ffe51a7157f2fbd2101 100644
--- a/components/mus/ws/display.h
+++ b/components/mus/ws/display.h
@@ -115,7 +115,9 @@ class Display : public PlatformDisplayDelegate,
 
   // 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();