views/mus: Add a test to verify that Widget receives events correctly.

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("//mojo/public/mojo_application.gni")
 import("//mojo/public/mojo_application_manifest.gni")
 import("//testing/test.gni")
 import("//tools/grit/repack.gni")
@@ skipping 168 matching lines @@
     "window_manager_connection_unittest.cc",
   ]
 
   deps = [
     ":mus",
     ":test_support",
     "//base",
     "//base:i18n",
     "//cc",
     "//components/mus/public/cpp",
+    "//components/mus/public/cpp/tests:unittest_support",
     "//components/mus/public/interfaces",
     "//services/shell/background:main",  # Provides main().
     "//skia",
     "//testing/gtest",
     "//third_party/icu",
     "//ui/accessibility",
     "//ui/aura",
     "//ui/aura:test_support",
     "//ui/base",
     "//ui/base:test_support",
@@ skipping 104 matching lines @@
 }
 
 group("for_component") {
   public_deps = [
     ":mus",
   ]
   deps = [
     "//mojo/gles2",
   ]
 }