(Merge to M-51) Revise the shelf alignment locking mechanism.

ash/shelf/shelf_util.h

 // Copyright 2013 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_SHELF_SHELF_UTIL_H_
 #define ASH_SHELF_SHELF_UTIL_H_
 
 #include "ash/ash_export.h"
 #include "ash/shelf/shelf_item_types.h"
+#include "ash/shelf/shelf_types.h"
 #include "base/strings/string16.h"
 #include "ui/aura/window.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ash {
 
 // A property key to store the id of the ShelfItem associated with the window.
@@ skipping 27 matching lines @@
 // Clears ShelfItemDetails for |window|.
 // If |window| has a ShelfItem by SetShelfItemDetailsForWindow(), it will
 // be removed.
 ASH_EXPORT void ClearShelfItemDetailsForWindow(aura::Window* window);
 
 // Returns ShelfItemDetails for |window| or NULL if it doesn't have.
 // Returned ShelfItemDetails object is owned by the |window|.
 ASH_EXPORT const ShelfItemDetails* GetShelfItemDetailsForWindow(
     aura::Window* window);
 
+// Returns true if the shelf |alignment| is horizontal.
+ASH_EXPORT bool IsHorizontalAlignment(ShelfAlignment alignment);
+
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_UTIL_H_