mash: Migrate [Keyboard]Brightness code to ash/common.

ash/test/ash_test_base.cc

 // Copyright (c) 2012 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.
 
 #include "ash/test/ash_test_base.h"
 
 #include <string>
 #include <vector>
 
 #include "ash/common/ash_switches.h"
+#include "ash/common/system/brightness_control_delegate.h"
 #include "ash/common/wm/window_positioner.h"
 #include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/ime/input_method_event_handler.h"
 #include "ash/shell.h"
 #include "ash/shell/toplevel_window.h"
 #include "ash/test/ash_test_helper.h"
 #include "ash/test/display_manager_test_api.h"
@@ skipping 331 matching lines @@
   SetUserAddingScreenRunning(false);
 }
 
 void AshTestBase::DisableIME() {
   Shell::GetInstance()->RemovePreTargetHandler(
       Shell::GetInstance()
           ->window_tree_host_manager()
           ->input_method_event_handler());
 }
 
+void AshTestBase::SetBrightnessControlDelegate(
+    std::unique_ptr<BrightnessControlDelegate> brightness_control_delegate) {
+  WmShell::Get()->SetBrightnessControlDelegate(
+      std::move(brightness_control_delegate));
+}
+
 }  // namespace test
 }  // namespace ash