Remove DisplayChangeObserver ash dependencies.

ash/display/screen_ash.cc

 // Copyright 2014 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 "ash/display/screen_ash.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shelf/shelf_widget.h"
 #include "ash/common/wm/root_window_finder.h"
+#include "ash/display/ash_display_string_provider.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/root_window_controller.h"
 #include "ash/root_window_settings.h"
 #include "ash/shell.h"
 #include "base/logging.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/display/display.h"
 #include "ui/display/display_finder.h"
@@ skipping 158 matching lines @@
 
 // static
 display::DisplayManager* ScreenAsh::CreateDisplayManager() {
   std::unique_ptr<ScreenAsh> screen(new ScreenAsh);
 
   display::Screen* current = display::Screen::GetScreen();
   // If there is no native, or the native was for shutdown,
   // use ash's screen.
   if (!current || current == screen_for_shutdown)
     display::Screen::SetScreenInstance(screen.get());
-  return new display::DisplayManager(std::move(screen));
+  return new display::DisplayManager(
+      std::move(screen), base::MakeUnique<AshDisplayStringProvider>());
 }
 
 // static
 void ScreenAsh::CreateScreenForShutdown() {
   delete screen_for_shutdown;
   screen_for_shutdown = new ScreenForShutdown(display::Screen::GetScreen());
   display::Screen::SetScreenInstance(screen_for_shutdown);
 }
 
 }  // namespace ash