views/mus: Install a mus-friend ContextFactory for tests.

ui/views/mus/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("//services/catalog/public/tools/catalog.gni")
 import("//services/service_manager/public/cpp/service.gni")
 import("//services/service_manager/public/service_manifest.gni")
 import("//testing/test.gni")
@@ skipping 110 matching lines @@
     "//base",
     "//base/test:test_support",
     "//mojo/edk/system",
     "//services/catalog:lib",
     "//services/service_manager/background:lib",
     "//services/service_manager/public/cpp:sources",
     "//services/ui/common:mus_common",
     "//testing/gtest",
     "//ui/aura",
     "//ui/aura:test_support",
+    "//ui/compositor:test_support",
     "//ui/gl:test_support",
     "//ui/resources",
     "//ui/resources:ui_test_pak",
     "//ui/views",
     "//ui/views:test_support_internal",
   ]
 
   data_deps = [
     ":views_mus_tests_catalog",
     "//ui/resources:ui_test_pak_data",
@@ skipping 153 matching lines @@
 copy("views_mus_tests_catalog_copy") {
   testonly = true
   sources = get_target_outputs(":views_mus_tests_catalog")
   outputs = [
     "${root_out_dir}/views_mus_tests_catalog.json",
   ]
   deps = [
     ":views_mus_tests_catalog",
   ]
 }