Updates shadow when active window changes

components/mus/public/cpp/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.
 
 source_set("cpp") {
   sources = [
     "context_provider.h",
     "event_matcher.h",
     "lib/context_provider.cc",
     "lib/event_matcher.cc",
@@ skipping 16 matching lines @@
     "scoped_window_ptr.h",
     "window.h",
     "window_manager_delegate.h",
     "window_observer.h",
     "window_property.h",
     "window_surface.h",
     "window_surface_client.h",
     "window_tracker.cc",
     "window_tracker.h",
     "window_tree_connection.h",
+    "window_tree_connection_observer.h",
     "window_tree_delegate.h",
     "window_tree_host_factory.h",
   ]
 
   public_deps = [
     "../interfaces",
     "//mojo/services/network/public/interfaces",
   ]
 
   deps = [
@@ skipping 16 matching lines @@
   ]
 
   data_deps = [
     "//components/mus",
   ]
 
   if (is_component_build) {
     deps += [ "//mojo/gles2" ]
   }
 }