Makes ash/wm/common a library

ash/wm/common/window_parenting_utils.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 ASH_WM_COMMON_WINDOW_PARENTING_UTILS_H_
 #define ASH_WM_COMMON_WINDOW_PARENTING_UTILS_H_
 
-#include "ash/ash_export.h"
-
 namespace ash {
 namespace wm {
 
 class WmWindow;
 
 // Changes the parent of a |child| and all its transient children that are
 // themselves children of |old_parent| to |new_parent|.
 void ReparentChildWithTransientChildren(WmWindow* child,
                                         WmWindow* old_parent,
                                         WmWindow* new_parent);
 
 // Changes the parent of all transient children of a |child| to |new_parent|.
 // Does not change parent of the transient children that are not themselves
 // children of |old_parent|.
 void ReparentTransientChildrenOfChild(WmWindow* child,
                                       WmWindow* old_parent,
                                       WmWindow* new_parent);
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_COMMON_WINDOW_PARENTING_UTILS_H_