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

ui/views/controls/combobox/combobox.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 "ui/views/controls/combobox/combobox.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "grit/ui_resources.h"
 #include "ui/base/accessibility/accessible_view_state.h"
@@ skipping 14 matching lines @@
 #include "ui/views/widget/widget.h"
 
 namespace views {
 
 namespace {
 
 // Menu border widths
 const int kMenuBorderWidthLeft = 1;
 const int kMenuBorderWidthTop = 1;
 const int kMenuBorderWidthRight = 1;
-const int kMenuBorderWidthBottom = 2;
 
 // Limit how small a combobox can be.
 const int kMinComboboxWidth = 25;
 
 // Size of the combobox arrow margins
 const int kDisclosureArrowLeftPadding = 7;
 const int kDisclosureArrowRightPadding = 7;
 
 // Define the id of the first item in the menu (since it needs to be > 0)
 const int kFirstMenuItemId = 1000;
@@ skipping 413 matching lines @@
 
 int Combobox::MenuCommandToIndex(int menu_command_id) const {
   // (note that the id received is offset by kFirstMenuItemId)
   // Revert menu ID offset to map back to combobox model.
   int index = menu_command_id - kFirstMenuItemId;
   DCHECK_LT(index, model()->GetItemCount());
   return index;
 }
 
 }  // namespace views