Change FocusSynchronizer to maintain active focus client and window.

ui/aura/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("aura") {
   sources = [
     "../wm/public/activation_change_observer.cc",
@@ skipping 61 matching lines @@
     "mus/capture_synchronizer.h",
     "mus/capture_synchronizer_delegate.h",
     "mus/client_surface_embedder.cc",
     "mus/client_surface_embedder.h",
     "mus/drag_drop_controller_host.h",
     "mus/drag_drop_controller_mus.cc",
     "mus/drag_drop_controller_mus.h",
     "mus/focus_synchronizer.cc",
     "mus/focus_synchronizer.h",
     "mus/focus_synchronizer_delegate.h",
+    "mus/focus_synchronizer_observer.h",
     "mus/in_flight_change.cc",
     "mus/in_flight_change.h",
     "mus/input_method_mus.cc",
     "mus/input_method_mus.h",
     "mus/mus_context_factory.cc",
     "mus/mus_context_factory.h",
     "mus/mus_mouse_location_updater.cc",
     "mus/mus_mouse_location_updater.h",
     "mus/mus_types.h",
     "mus/os_exchange_data_provider_mus.cc",
@@ skipping 283 matching lines @@
   ]
 
   if (is_linux) {
     deps += [ "//third_party/mesa" ]
   }
 
   data_deps = [
     "//third_party/mesa:osmesa",
   ]
 }