Makes SetFocus() notify callback correctly on failure

components/mus/ws/focus_controller.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_FOCUS_CONTROLLER_H_
 #define COMPONENTS_MUS_WS_FOCUS_CONTROLLER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
@@ skipping 17 matching lines @@
 };
 
 // Tracks the focused window. Focus is moved to another window when the drawn
 // state of the focused window changes.
 class FocusController : public ServerWindowDrawnTrackerObserver {
  public:
   FocusController(FocusControllerDelegate* delegate, ServerWindow* root);
   ~FocusController() override;
 
   // Sets the focused window. Does nothing if |window| is currently focused.
-  // This does not notify the delegate.
-  void SetFocusedWindow(ServerWindow* window);
+  // This does not notify the delegate. See ServerWindow::SetFocusedWindow()
+  // for details on return value.
+  bool SetFocusedWindow(ServerWindow* window);
   ServerWindow* GetFocusedWindow();
 
   // Moves activation to the next activatable window.
   void ActivateNextWindow();
 
   void AddObserver(FocusControllerObserver* observer);
   void RemoveObserver(FocusControllerObserver* observer);
 
  private:
   enum class ActivationChangeReason {
     UNKNONW,
     CYCLE,  // Activation changed because of ActivateNextWindow().
     FOCUS,  // Focus change required a different window to be activated.
     DRAWN_STATE_CHANGED,  // Active window was hidden or destroyed.
   };
   void SetActiveWindow(ServerWindow* window, ActivationChangeReason reason);
 
   // Returns whether |window| can be focused or activated.
   bool CanBeFocused(ServerWindow* window) const;
   bool CanBeActivated(ServerWindow* window) const;
 
   // Returns the closest activatable ancestor of |window|. Returns nullptr if
   // there is no such ancestor.
   ServerWindow* GetActivatableAncestorOf(ServerWindow* window) const;
 
   // Implementation of SetFocusedWindow().
-  void SetFocusedWindowImpl(FocusControllerChangeSource change_source,
+  bool SetFocusedWindowImpl(FocusControllerChangeSource change_source,
                             ServerWindow* window);
 
   // ServerWindowDrawnTrackerObserver:
   void OnDrawnStateWillChange(ServerWindow* ancestor,
                               ServerWindow* window,
                               bool is_drawn) override;
   void OnDrawnStateChanged(ServerWindow* ancestor,
                            ServerWindow* window,
                            bool is_drawn) override;
 
@@ skipping 16 matching lines @@
   scoped_ptr<ServerWindowDrawnTracker> drawn_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(FocusController);
 };
 
 }  // namespace ws
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_FOCUS_CONTROLLER_H_