Use the source display's pixel size as a mirror window's size.

ash/display/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 ASH_DISPLAY_DISPLAY_MANAGER_H_
 #define ASH_DISPLAY_DISPLAY_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 125 matching lines @@
   // Returns the logical number of displays. This returns 1
   // when displays are mirrored.
   size_t GetNumDisplays() const;
 
   // Returns the number of connected displays. This returns 2
   // when displays are mirrored.
   size_t num_connected_displays() const { return num_connected_displays_; }
 
   // Returns the mirroring status.
   bool IsMirrored() const;
-  int64 mirrored_display_id() const { return mirrored_display_.id(); }
+  const gfx::Display& mirrored_display() const { return mirrored_display_; }
 
   // Returns the display object nearest given |window|.
   const gfx::Display& GetDisplayNearestPoint(
       const gfx::Point& point) const;
 
   // Returns the display object nearest given |point|.
   const gfx::Display& GetDisplayNearestWindow(
       const aura::Window* window) const;
 
   // Returns the display that most closely intersects |match_rect|.
@@ skipping 46 matching lines @@
 
   void set_change_display_upon_host_resize(bool value) {
     change_display_upon_host_resize_ = value;
   }
 
   void Init();
 
   gfx::Display& FindDisplayForRootWindow(const aura::RootWindow* root);
   gfx::Display& FindDisplayForId(int64 id);
 
+  // Add the mirror display's display info if the software based
+  // mirroring is in use.
+  void AddMirrorDisplayInfoIfAny(std::vector<DisplayInfo>* display_info_list);
+
   // Refer to |CreateDisplayFromSpec| API for the format of |spec|.
   void AddDisplayFromSpec(const std::string& spec);
 
   // Inserts and update the DisplayInfo according to the overscan
   // state. Note that The DisplayInfo stored in the |internal_display_info_|
   // can be different from |new_info| (due to overscan state), so
   // you must use |GetDisplayInfo| to get the correct DisplayInfo for
   // a display.
   void InsertAndUpdateDisplayInfo(const DisplayInfo& new_info);
 
@@ skipping 25 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DisplayManager);
 };
 
 extern const aura::WindowProperty<int64>* const kDisplayIdKey;
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_DISPLAY_MANAGER_H_