Fixes shutdown race in mash

ash/mus/BUILD.gn

 # Copyright 2015 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("//mojo/public/mojo_application.gni")
 import("//mojo/public/mojo_application_manifest.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//tools/grit/repack.gni")
 
@@ skipping 36 matching lines @@
     "frame/non_client_frame_view_mash.cc",
     "frame/non_client_frame_view_mash.h",
     "layout_manager.cc",
     "layout_manager.h",
     "non_client_frame_controller.cc",
     "non_client_frame_controller.h",
     "property_util.cc",
     "property_util.h",
     "root_window_controller.cc",
     "root_window_controller.h",
-    "root_windows_observer.h",
     "screenlock_layout.cc",
     "screenlock_layout.h",
     "shadow.cc",
     "shadow.h",
     "shadow_controller.cc",
     "shadow_controller.h",
     "shelf_layout_impl.cc",
     "shelf_layout_impl.h",
     "shelf_layout_manager.cc",
     "shelf_layout_manager.h",
     "shelf_layout_manager_delegate.h",
     "status_layout_manager.cc",
     "status_layout_manager.h",
     "user_window_controller_impl.cc",
     "user_window_controller_impl.h",
     "window_manager.cc",
     "window_manager.h",
     "window_manager_application.cc",
     "window_manager_application.h",
+    "window_manager_observer.h",
   ]
 
   deps = [
     "//components/user_manager",
   ]
 
   public_deps = [
     "//ash",
     "//ash/mus/resources",
     "//ash/public/interfaces",
@@ skipping 109 matching lines @@
     "//ui/gfx/geometry",
     "//ui/gfx/geometry/mojo",
     "//ui/views/mus",
   ]
 
   data_deps = [
     ":mus",
     "//mash/quick_launch",
   ]
 }