ui: Cleanup class/struct forward declarations

ui/platform_window/android/platform_window_android.h

 // Copyright 2013 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_PLATFORM_WINDOW_ANDROID_PLATFORM_WINDOW_ANDROID_H_
 #define UI_PLATFORM_WINDOW_ANDROID_PLATFORM_WINDOW_ANDROID_H_
 
 #include "base/android/jni_weak_ref.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "ui/events/event_constants.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/sequential_id_generator.h"
 #include "ui/platform_window/android/android_window_export.h"
 #include "ui/platform_window/android/platform_ime_controller_android.h"
 #include "ui/platform_window/platform_window.h"
 
 struct ANativeWindow;
 
 namespace ui {
 
+class PlatformWindowDelegate;
+
 class ANDROID_WINDOW_EXPORT PlatformWindowAndroid : public PlatformWindow {
  public:
   static bool Register(JNIEnv* env);
 
   explicit PlatformWindowAndroid(PlatformWindowDelegate* delegate);
   ~PlatformWindowAndroid() override;
 
   void Destroy(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
   void SurfaceCreated(JNIEnv* env,
                       const base::android::JavaParamRef<jobject>& obj,
@@ skipping 57 matching lines @@
   PlatformImeControllerAndroid platform_ime_controller_;
 
   base::WeakPtrFactory<PlatformWindowAndroid> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformWindowAndroid);
 };
 
 }  // namespace ui
 
 #endif  // UI_PLATFORM_WINDOW_ANDROID_PLATFORM_WINDOW_ANDROID_H_