ui: Cleanup class/struct forward declarations

ui/ozone/platform/wayland/wayland_window.h

 // Copyright 2016 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_OZONE_PLATFORM_WAYLAND_WAYLAND_WINDOW_H_
 #define UI_OZONE_PLATFORM_WAYLAND_WAYLAND_WINDOW_H_
 
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/wayland/wayland_object.h"
 #include "ui/platform_window/platform_window.h"
 
 namespace ui {
 
+class PlatformWindowDelegate;
 class WaylandConnection;
 
 class WaylandWindow : public PlatformWindow, public PlatformEventDispatcher {
  public:
   WaylandWindow(PlatformWindowDelegate* delegate,
                 WaylandConnection* connection,
                 const gfx::Rect& bounds);
   ~WaylandWindow() override;
 
   static WaylandWindow* FromSurface(wl_surface* surface);
@@ skipping 51 matching lines @@
   gfx::Rect pending_bounds_;
   uint32_t pending_configure_serial_;
   bool has_pointer_focus_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WaylandWindow);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_WAYLAND_WAYLAND_WINDOW_H_