ash: Cleanup class/struct forward declarations

ash/common/system/tray/tray_utils.h

 // 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.
 
 #ifndef ASH_COMMON_SYSTEM_TRAY_TRAY_UTILS_H_
 #define ASH_COMMON_SYSTEM_TRAY_TRAY_UTILS_H_
 
 #include <vector>
 
 #include "ash/public/cpp/shelf_types.h"
 #include "base/strings/string16.h"
 
 namespace views {
 class Label;
-class Separator;
 class View;
 }
 
 namespace ash {
 
 class TrayItemView;
 
 // Sets up a Label properly for the tray (sets color, font etc.).
 void SetupLabelForTray(views::Label* label);
 
 // TODO(jennyz): refactor these two functions to SystemTrayItem.
 // Sets the empty border of an image tray item for adjusting the space
 // around it.
 void SetTrayImageItemBorder(views::View* tray_view, ShelfAlignment alignment);
 // Sets the empty border around a label tray item for adjusting the space
 // around it.
 void SetTrayLabelItemBorder(TrayItemView* tray_view, ShelfAlignment alignment);
 
 // Computes an accessible label for this button based on all descendant view
 // labels by concatenating them in depth-first order.
 void GetAccessibleLabelFromDescendantViews(
     views::View* view,
     std::vector<base::string16>& out_labels);
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_UTILS_H_