Ensure fake alert window attached to AXAura tree and refine alert dialog output

chrome/browser/ui/aura/accessibility/ax_root_obj_wrapper.cc

 // Copyright 2014 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 "chrome/browser/ui/aura/accessibility/ax_root_obj_wrapper.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/aura/window.h"
@@ skipping 28 matching lines @@
   return std::find(children.begin(), children.end(), child) != children.end();
 }
 
 views::AXAuraObjWrapper* AXRootObjWrapper::GetParent() {
   return NULL;
 }
 
 void AXRootObjWrapper::GetChildren(
     std::vector<views::AXAuraObjWrapper*>* out_children) {
   views::AXAuraObjCache::GetInstance()->GetTopLevelWindows(out_children);
+  out_children->push_back(
+      views::AXAuraObjCache::GetInstance()->GetOrCreate(alert_window_));
 }
 
 void AXRootObjWrapper::Serialize(ui::AXNodeData* out_node_data) {
   out_node_data->id = id_;
   out_node_data->role = ui::AX_ROLE_DESKTOP;
   // TODO(dtseng): Apply a richer set of states.
   out_node_data->state = 0;
 }
 
 int32_t AXRootObjWrapper::GetID() {
   return id_;
 }