linux and chromeos: Turn on -Wunused-const-variable.

ash/system/tray_accessibility.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_accessibility.h"
 
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
 #include "ash/system/tray/hover_highlight_view.h"
 #include "ash/system/tray/system_tray.h"
@@ skipping 11 matching lines @@
 #include "ui/gfx/image/image.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace internal {
 
 namespace {
-const int kPaddingAroundBottomRow = 5;
 
 enum AccessibilityState {
   A11Y_NONE             = 0,
   A11Y_SPOKEN_FEEDBACK  = 1 << 0,
   A11Y_HIGH_CONTRAST    = 1 << 1,
   A11Y_SCREEN_MAGNIFIER = 1 << 2,
   A11Y_LARGE_CURSOR     = 1 << 3,
 };
 
 uint32 GetAccessibilityState() {
@@ skipping 303 matching lines @@
       detailed_popup_->GetWidget()->Close();
     if (detailed_menu_)
       detailed_menu_->GetWidget()->Close();
   }
 
   previous_accessibility_state_ = accessibility_state;
 }
 
 }  // namespace internal
 }  // namespace ash