Adds ability for ash_unittests to run in mushrome mode

ash/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/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 # Historical note: Ash shipped on Windows for a couple years to support
@@ skipping 1097 matching lines @@
     "//content/public/browser",
     "//content/test:test_support",
     "//device/bluetooth",
     "//mojo/edk/system",
     "//net",
     "//skia",
     "//testing/gtest",
     "//ui/aura",
     "//ui/aura:test_support",
     "//ui/chromeos",
+    "//ui/compositor:test_support",
     "//ui/display",
     "//ui/display:test_support",
     "//ui/gl:test_support",
     "//ui/message_center",
     "//ui/message_center:test_support",
     "//ui/views",
     "//ui/views:test_support",
     "//ui/views/controls/webview:test_support",
     "//ui/web_dialogs:test_support",
   ]
@@ skipping 366 matching lines @@
     "//content/public/app:both",
     "//device/bluetooth",
   ]
 
   data_deps = [
     "//ash/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_with_content_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }