Add ability to set resolution on external display

ash/display/display_change_observer_x11.h

Index: ash/display/display_change_observer_x11.h
diff --git a/ash/display/display_change_observer_x11.h b/ash/display/display_change_observer_x11.h
index 3d13e0d0147c44d71ccfe21a6d6f4edb872dab8e..67811515b19af5665c755790bf5f0ccbcf422eea 100644
--- a/ash/display/display_change_observer_x11.h
+++ b/ash/display/display_change_observer_x11.h
@@ -31,6 +31,9 @@ class DisplayChangeObserverX11
   // chromeos::OutputConfigurator::StateController overrides:
   virtual chromeos::OutputState GetStateForDisplayIds(
       const std::vector<int64>& outputs) const OVERRIDE;
+  virtual bool GetResolutionForDisplayId(int64 display_id,
+                                         int* width,
+                                         int* height) const OVERRIDE;
 
   // Overriden from chromeos::OutputConfigurator::Observer:
   virtual void OnDisplayModeChanged() OVERRIDE;
@@ -48,12 +51,6 @@ class DisplayChangeObserverX11
   DISALLOW_COPY_AND_ASSIGN(DisplayChangeObserverX11);
 };
 
-// Returns true if the size info in the output_info isn't valid
-// and should be ignored. This is exposed for testing.
-// |mm_width| and |mm_height| are given in millimeters.
-ASH_EXPORT bool ShouldIgnoreSize(unsigned long mm_width,
-                                 unsigned long mm_height);
-
 }  // namespace internal
 }  // namespace ash