ui: Cleanup class/struct forward declarations

ui/aura/test/aura_test_helper.h

 // 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.
 
 #ifndef UI_AURA_TEST_AURA_TEST_HELPER_H_
 #define UI_AURA_TEST_AURA_TEST_HELPER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_tree_host.h"
 
 namespace base {
 class MessageLoopForUI;
 }
 
 namespace ui {
 class ContextFactory;
-class InputMethod;
 class ScopedAnimationDurationScaleMode;
 }
 
 namespace wm {
 class WMState;
 }
 
 namespace aura {
 class Env;
 class TestScreen;
@@ skipping 96 matching lines @@
 
   WindowTreeClient* window_tree_client_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(AuraTestHelper);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_AURA_TEST_HELPER_H_