Remove DisplayChangeObserver ash dependencies.

ui/display/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 component("display") {
   sources = [
     "chromeos/apply_content_protection_task.cc",
@@ skipping 35 matching lines @@
     "manager/display_layout.cc",
     "manager/display_layout.h",
     "manager/display_layout_builder.cc",
     "manager/display_layout_builder.h",
     "manager/display_layout_store.cc",
     "manager/display_layout_store.h",
     "manager/display_manager.cc",
     "manager/display_manager.h",
     "manager/display_manager_utilities.cc",
     "manager/display_manager_utilities.h",
+    "manager/display_string_provider.h",
     "manager/managed_display_info.cc",
     "manager/managed_display_info.h",
     "screen.cc",
     "screen.h",
     "screen_aura.cc",
     "screen_base.cc",
     "screen_base.h",
     "win/display_info.cc",
     "win/display_info.h",
     "win/dpi.cc",
@@ skipping 161 matching lines @@
     sources -= [ "display_change_notifier_unittest.cc" ]
   }
 
   if (is_chromeos && use_x11) {
     sources += [
       "chromeos/x11/display_util_x11_unittest.cc",
       "chromeos/x11/native_display_event_dispatcher_x11_unittest.cc",
     ]
   }
 }