Enable chrome.automation.getDesktop on all aura platforms.

chrome/browser/ui/ash/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/ash/accessibility/ax_root_obj_wrapper.h"
 
-#include "ash/shell.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/ax_view_state.h"
 #include "ui/aura/window.h"
+#include "ui/aura/window_tree_host.h"
 #include "ui/views/accessibility/ax_aura_obj_cache.h"
 #include "ui/views/accessibility/ax_window_obj_wrapper.h"
 
+#if defined(OS_CHROMEOS)
+#include "ash/shell.h"
+#endif
+
 AXRootObjWrapper::AXRootObjWrapper(int32 id)
     : id_(id), alert_window_(new aura::Window(NULL)) {
 }
 
 AXRootObjWrapper::~AXRootObjWrapper() {
   if (alert_window_) {
     delete alert_window_;
     alert_window_ = NULL;
   }
 }
@@ skipping 13 matching lines @@
   GetChildren(&children);
   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) {
-  if (!ash::Shell::HasInstance())
-    return;
-
-  // Only on ash is there a notion of a root with children.
+#if defined(OS_CHROMEOS)

[oshima, 2015/03/20 22:31:42]

I still don't quite understand why you need this.

When/how you're getting null shell? Do you have the stack trace?

The only way you can get null shell is when you run Windows in desktop mode
only. (no WinAsh) but If you're not on ash, this method shouldn't be called?

   aura::Window::Windows children =
       ash::Shell::GetInstance()->GetAllRootWindows();
   for (size_t i = 0; i < children.size(); ++i) {
     out_children->push_back(
         views::AXAuraObjCache::GetInstance()->GetOrCreate(children[i]));
   }
 
   out_children->push_back(
       views::AXAuraObjCache::GetInstance()->GetOrCreate(alert_window_));
+#else
+  views::AXAuraObjCache::GetInstance()->GetTopLevelWindows(out_children);
+#endif
 }
 
 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 AXRootObjWrapper::GetID() {
   return id_;
 }