Use correct position when setting pos_in_set for tabs.

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 <stddef.h>
 
 #include <utility>
 
@@ skipping 743 matching lines @@
 }
 
 void Combobox::GetAccessibleNodeData(ui::AXNodeData* node_data) {
   node_data->role = ui::AX_ROLE_COMBO_BOX;
   node_data->SetName(accessible_name_);
   node_data->SetValue(model_->GetItemAt(selected_index_));
   if (enabled()) {
     node_data->AddIntAttribute(ui::AX_ATTR_ACTION,
                                ui::AX_SUPPORTED_ACTION_OPEN);
   }
-  node_data->AddIntAttribute(ui::AX_ATTR_POS_IN_SET, selected_index_);
+  node_data->AddValidatedIntAttribute(ui::AX_ATTR_INDEX_IN_SET,
+                                      selected_index_);
   node_data->AddIntAttribute(ui::AX_ATTR_SET_SIZE, model_->GetItemCount());
 }
 
 void Combobox::ButtonPressed(Button* sender, const ui::Event& event) {
   if (!enabled())
     return;
 
   if (!UseMd())
     RequestFocus();
 
@@ skipping 238 matching lines @@
   const int kMdPaddingWidth = 8;
   int arrow_pad = UseMd() ? kMdPaddingWidth
                           : PlatformStyle::kComboboxNormalArrowPadding;
   int padding = style_ == STYLE_NORMAL
                     ? arrow_pad * 2
                     : kActionLeftPadding + kActionRightPadding;
   return ArrowSize().width() + padding;
 }
 
 }  // namespace views