Introduce aura::Env controller to abstract away changes to aura::Env

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 55 matching lines @@
     "layout_manager.h",
     "mus/mus_util.cc",
     "mus/mus_util.h",
     "scoped_window_targeter.cc",
     "scoped_window_targeter.h",
     "window.cc",
     "window.h",
     "window_delegate.h",
     "window_event_dispatcher.cc",
     "window_event_dispatcher.h",
+    "window_event_dispatcher_delegate.cc",
+    "window_event_dispatcher_delegate.h",
     "window_observer.cc",
     "window_observer.h",
     "window_targeter.cc",
     "window_targeter.h",
     "window_tracker.h",
     "window_tree_host.cc",
     "window_tree_host.h",
     "window_tree_host_mac.h",
     "window_tree_host_mac.mm",
     "window_tree_host_observer.h",
@@ skipping 190 matching lines @@
   ]
 
   if (is_linux) {
     deps += [ "//third_party/mesa" ]
   }
 
   data_deps = [
     "//third_party/mesa:osmesa",
   ]
 }