Update desktop tree when Aura windows are removed.

ui/views/accessibility/ax_widget_obj_wrapper.cc

Index: ui/views/accessibility/ax_widget_obj_wrapper.cc
diff --git a/ui/views/accessibility/ax_widget_obj_wrapper.cc b/ui/views/accessibility/ax_widget_obj_wrapper.cc
index 1def13f922d9884643c01560fd622e8bf6101eca..2a05b196651cacf5c8be03fd4d29184cd025ac11 100644
--- a/ui/views/accessibility/ax_widget_obj_wrapper.cc
+++ b/ui/views/accessibility/ax_widget_obj_wrapper.cc
@@ -58,6 +58,10 @@ void AXWidgetObjWrapper::OnWidgetDestroying(Widget* widget) {
   AXAuraObjCache::GetInstance()->Remove(widget);
 }
 
+void AXWidgetObjWrapper::OnWidgetClosing(Widget* widget) {
+  AXAuraObjCache::GetInstance()->Remove(widget);
+}
+
 void AXWidgetObjWrapper::OnWillRemoveView(Widget* widget, View* view) {
   AXAuraObjCache::GetInstance()->RemoveViewSubtree(view);
 }