Close mirroring window only when necessary

ash/display/display_controller.h

 // Copyright (c) 2012 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 ASH_DISPLAY_DISPLAY_CONTROLLER_H_
 #define ASH_DISPLAY_DISPLAY_CONTROLLER_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 141 matching lines @@
   void OnDisplayRemoved(const gfx::Display& display) override;
   void OnDisplayMetricsChanged(const gfx::Display& display,
                                uint32_t metrics) override;
 
   // aura::WindowTreeHostObserver overrides:
   void OnHostResized(const aura::WindowTreeHost* host) override;
 
   // aura::DisplayManager::Delegate overrides:
   void CreateOrUpdateMirroringDisplay(
       const DisplayInfoList& info_list) override;
-  void CloseMirroringDisplay() override;
+  void CloseMirroringDisplayIfNotNecessary() override;
   void PreDisplayConfigurationChange(bool clear_focus) override;
   void PostDisplayConfigurationChange() override;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(DisplayControllerTest, BoundsUpdated);
   FRIEND_TEST_ALL_PREFIXES(DisplayControllerTest, SecondaryDisplayLayout);
   friend class DisplayManager;
   friend class MirrorWindowController;
 
   // Creates a WindowTreeHost for |display| and stores it in the
@@ skipping 57 matching lines @@
   int64 cursor_display_id_for_restore_;
 
   base::WeakPtrFactory<DisplayController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_DISPLAY_CONTROLLER_H_