Revise the shelf alignment locking mechanism.

ash/system/tray/tray_image_item.cc

 // Copyright (c) 2012 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.
 
 #include "ash/system/tray/tray_image_item.h"
 
+#include "ash/shelf/shelf_util.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/tray_item_view.h"
 #include "ash/system/tray/tray_utils.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/layout/box_layout.h"
 
 namespace ash {
 
@@ skipping 49 matching lines @@
 }
 
 void TrayImageItem::DestroyDefaultView() {
 }
 
 void TrayImageItem::DestroyDetailedView() {
 }
 
 void TrayImageItem::SetItemAlignment(ShelfAlignment alignment) {
   // Center the item dependent on the orientation of the shelf.
-  views::BoxLayout::Orientation layout = views::BoxLayout::kHorizontal;
-  switch (alignment) {
-    case ash::SHELF_ALIGNMENT_BOTTOM:
-      layout = views::BoxLayout::kHorizontal;
-      break;
-    case ash::SHELF_ALIGNMENT_LEFT:
-    case ash::SHELF_ALIGNMENT_RIGHT:
-      layout = views::BoxLayout::kVertical;
-      break;
-  }
+  views::BoxLayout::Orientation layout = IsHorizontalAlignment(alignment)
+                                             ? views::BoxLayout::kHorizontal
+                                             : views::BoxLayout::kVertical;
   tray_view_->SetLayoutManager(new views::BoxLayout(layout, 0, 0, 0));
   tray_view_->Layout();
 }
 
 }  // namespace ash