Makes ash/wm/common a library

ash/wm/common/window_state_util.h

 // Copyright 2014 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 ASH_WM_COMMON_WINDOW_STATE_UTIL_H_
 #define ASH_WM_COMMON_WINDOW_STATE_UTIL_H_
 
+#include "ash/wm/common/ash_wm_common_export.h"
+
 namespace ash {
 namespace wm {
 class WindowState;
 class WindowStateDelegate;
 
 // Toggle the full screen from inside a WindowState::State handler.
-void ToggleFullScreen(WindowState* window_state, WindowStateDelegate* delegate);
+ASH_WM_COMMON_EXPORT void ToggleFullScreen(WindowState* window_state,
+                                           WindowStateDelegate* delegate);
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_COMMON_WINDOW_STATE_UTIL_H_