Add ability to set resolution on external display

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 112 matching lines @@
   // that the insets size should be specified in DIP size. It also triggers the
   // display's bounds change.
   void SetOverscanInsets(int64 display_id, const gfx::Insets& insets_in_dip);
 
   // Sets the display's rotation.
   void SetDisplayRotation(int64 display_id, gfx::Display::Rotation rotation);
 
   // Sets the display's ui scale.
   void SetDisplayUIScale(int64 display_id, float ui_scale);
 
+  // Sets the display's resolution.
+  void SetDisplayResolution(int64 display_id, const gfx::Size& resolution);
+
   // Register per display properties. |overscan_insets| is NULL if
   // the display has no custom overscan insets.
   void RegisterDisplayProperty(int64 display_id,
                                gfx::Display::Rotation rotation,
                                float ui_scale,
-                               const gfx::Insets* overscan_insets);
+                               const gfx::Insets* overscan_insets,
+                               const gfx::Size& resolution_in_pixels);
+
+  // Returns the display's selected resolution.
+  bool GetSelectedResolutionForDisplayId(int64 display_id,
+                                         gfx::Size* resolution_out) const;
 
   // Tells if display rotation/ui scaling features are enabled.
   bool IsDisplayRotationEnabled() const;
   bool IsDisplayUIScalingEnabled() const;
 
   // Returns the current overscan insets for the specified |display_id|.
   // Returns an empty insets (0, 0, 0, 0) if no insets are specified for
   // the display.
   gfx::Insets GetOverscanInsets(int64 display_id) const;
 
@@ skipping 114 matching lines @@
   // List of current active dispays.
   DisplayList displays_;
 
   int num_connected_displays_;
 
   bool force_bounds_changed_;
 
   // The mapping from the display ID to its internal data.
   std::map<int64, DisplayInfo> display_info_;
 
+  // Selected resolutions for displays. Key is the displays' ID.
+  std::map<int64, gfx::Size> resolutions_;
+
   // When set to true, the host window's resize event updates
   // the display's size. This is set to true when running on
   // desktop environment (for debugging) so that resizing the host
   // window wil update the display properly. This is set to false
   // on device as well as during the unit tests.
   bool change_display_upon_host_resize_;
 
   bool software_mirroring_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_DISPLAY_MANAGER_H_