wayland: forward declare WaylandEvent

base/event_types.h

 // Copyright (c) 2011 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 BASE_EVENT_TYPES_H
 #define BASE_EVENT_TYPES_H
 #pragma once
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(USE_WAYLAND)
-#include "base/wayland/wayland_event.h"
+namespace base {
+namespace wayland {
+union WaylandEvent;
+}
+}
 #elif defined(USE_X11)
 typedef union _XEvent XEvent;
 #endif
 
 namespace base {
 
 // Cross platform typedefs for native event types.
 #if defined(OS_WIN)
 typedef MSG NativeEvent;
 #elif defined(USE_WAYLAND)
 typedef wayland::WaylandEvent* NativeEvent;
 #elif defined(USE_X11)
 typedef XEvent* NativeEvent;
 #else
 typedef void* NativeEvent;
 #endif
 
 } // namespace base
 
 #endif  // BASE_EVENT_TYPES_H