ui: Cleanup class/struct forward declarations

ui/aura/window_delegate.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_WINDOW_DELEGATE_H_
 #define UI_AURA_WINDOW_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "ui/aura/aura_export.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_handler.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
-class Canvas;
 class Path;
 class Point;
 class Rect;
 class Size;
 }
 
 namespace ui {
-class GestureEvent;
-class KeyEvent;
-class Layer;
-class MouseEvent;
 class PaintContext;
-class TextInputClient;
-class Texture;
-class TouchEvent;
 }
 
 namespace aura {
 
 // Delegate interface for aura::Window.
 class AURA_EXPORT WindowDelegate : public ui::EventHandler {
  public:
   // Returns the window's minimum size, or size 0,0 if there is no limit.
   virtual gfx::Size GetMinimumSize() const = 0;
 
@@ skipping 63 matching lines @@
   // Sent when the server requests the window to close.
   virtual void OnRequestClose();
 
  protected:
   ~WindowDelegate() override {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_DELEGATE_H_