Move Screen, its impls, DisplayObserver and DisplayChangeNotifier to ui/display

ui/gfx/display_observer.cc

Index: ui/gfx/display_observer.cc
diff --git a/ui/gfx/display_observer.cc b/ui/gfx/display_observer.cc
deleted file mode 100644
index f8e3c07640164e35c05b76337238ab49eecb59cd..0000000000000000000000000000000000000000
--- a/ui/gfx/display_observer.cc
+++ /dev/null
@@ -1,12 +0,0 @@
-// 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/display_observer.h"
-
-namespace gfx {
-
-DisplayObserver::~DisplayObserver() {
-}
-
-}  // namespace gfx