Display: dectect changes to mirror mode and send a notification.

ui/display/manager/display_manager.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 UI_DISPLAY_MANAGER_DISPLAY_MANAGER_H_
 #define UI_DISPLAY_MANAGER_DISPLAY_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 453 matching lines @@
   // debugging) so that resizing the host window will update the display
   // properly. This is set to false on device as well as during the unit tests.
   bool change_display_upon_host_resize_ = false;
 
   MultiDisplayMode multi_display_mode_ = EXTENDED;
   MultiDisplayMode current_default_multi_display_mode_ = EXTENDED;
 
   int64_t mirroring_display_id_ = kInvalidDisplayId;
   Displays software_mirroring_display_list_;
 
+  // Cached mirror mode for metrics changed notification.
+  bool mirror_mode_for_metrics_ = false;
+
   // User preference for rotation lock of the internal display.
   bool registered_internal_display_rotation_lock_ = false;
 
   // User preference for the rotation of the internal display.
   Display::Rotation registered_internal_display_rotation_ = Display::ROTATE_0;
 
   bool unified_desktop_enabled_ = false;
 
   base::ObserverList<DisplayObserver> observers_;
 
   base::WeakPtrFactory<DisplayManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayManager);
 };
 
 }  // namespace display
 
 #endif  // UI_DISPLAY_MANAGER_DISPLAY_MANAGER_H_