mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/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")
 import("//mojo/public/mojo_application.gni")
 import("//mojo/public/mojo_application_manifest.gni")
 
 source_set("lib") {
   sources = [
     "accelerator.cc",
     "accelerator.h",
     "access_policy.h",
     "access_policy_delegate.h",
     "default_access_policy.cc",
     "default_access_policy.h",
     "display.cc",
     "display.h",
     "display_binding.cc",
     "display_binding.h",
     "display_manager.cc",
     "display_manager.h",
     "display_manager_delegate.h",
     "event_dispatcher.cc",
     "event_dispatcher.h",
     "event_dispatcher_delegate.h",
+    "event_tester.cc",
+    "event_tester.h",
     "focus_controller.cc",
     "focus_controller.h",
     "focus_controller_delegate.h",
     "focus_controller_observer.h",
     "operation.cc",
     "operation.h",
     "platform_display.cc",
     "platform_display.h",
     "platform_display_delegate.h",
     "platform_display_factory.h",
@@ skipping 105 matching lines @@
   if (!is_android) {
     deps +=
         [ "//components/mus/public/cpp/tests:mojo_view_manager_lib_unittests" ]
   }
 }
 
 test("mus_ws_unittests") {
   sources = [
     "display_unittest.cc",
     "event_dispatcher_unittest.cc",
+    "event_tester_unittest.cc",
     "focus_controller_unittest.cc",
     "server_window_drawn_tracker_unittest.cc",
     "server_window_surface_manager_test_api.cc",
     "server_window_surface_manager_test_api.h",
     "test_server_window_delegate.cc",
     "test_server_window_delegate.h",
     "test_utils.cc",
     "test_utils.h",
     "transient_windows_unittest.cc",
     "user_display_manager_unittest.cc",
@@ skipping 48 matching lines @@
 
   data_deps = [
     ":mus_ws_unittests_app_manifest",
   ]
 }
 
 mojo_application_manifest("mus_ws_unittests_app_manifest") {
   application_name = "mus_ws_unittests_app"
   source = "mus_ws_unittests_app_manifest.json"
 }