Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/gfx/screen_android.cc

 // 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.
 
 #include "ui/gfx/screen.h"
 
 #include "base/logging.h"
 #include "ui/gfx/display.h"
 
 namespace gfx {
@@ skipping 30 matching lines @@
 
   int GetNumDisplays() OVERRIDE {
     return 1;
   }
 
   virtual gfx::Display GetDisplayMatching(
       const gfx::Rect& match_rect) const OVERRIDE {
     return GetPrimaryDisplay();
   }
 
+  virtual void AddObserver(DisplayObserver* observer) OVERRIDE {
+    // no display change on Android.
+  }
+
+  virtual void RemoveObserver(DisplayObserver* observer) OVERRIDE {
+    // no display change on Android.
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(ScreenAndroid);
 };
 
 Screen* CreateNativeScreen() {
   return new ScreenAndroid;
 }
 
 }  // namespace gfx