Move CycleDirection enum into shelf_constants.

ash/shelf/shelf_constants.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_CONSTANTS_H_
 #define ASH_SHELF_SHELF_CONSTANTS_H_
 
 #include "ash/ash_export.h"
 
 namespace ash {
 
 // Height of the shelf. Hard coded to avoid resizing as items are added/removed.
 ASH_EXPORT extern const int kShelfPreferredSize;
 
 // Max alpha of the shelf background.
 ASH_EXPORT extern const int kShelfBackgroundAlpha;
 
 // Invalid image resource id used for LauncherItemDetails.
 extern const int kInvalidImageResourceID;
 
 extern const int kInvalidShelfID;
 
 // Animation duration for switching black shelf and dock background on and off.
 ASH_EXPORT extern const int kTimeToSwitchBackgroundMs;
 
+// The direction of the focus cycling.
+enum CycleDirection {
+  CYCLE_FORWARD,
+  CYCLE_BACKWARD
+};
+
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_CONSTANTS_H_