Add kAccessibilityFocusFallsbackToWidget property

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index b14dce1f8f4eeb69271a7dee479816ac5e22ae10..76ecacda8c99f228d2dcb7a7a335552db85ef362 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -331,6 +331,9 @@ void Widget::Init(const InitParams& in_params) {
   ownership_ = params.ownership;
   native_widget_ = CreateNativeWidget(params, this)->AsNativeWidgetPrivate();
   root_view_.reset(CreateRootView());
+  // Make root view of widget accessibility focusable as automation can fire
+  // focus change event to it.
+  root_view_->SetFocusBehavior(View::FocusBehavior::ACCESSIBLE_ONLY);

[sky, 2016/12/01 00:36:59]

Again, might this result in trying to focus widgets that we normally don't want
focused?

[yawano, 2016/12/01 00:47:08]

Yes.

   default_theme_provider_.reset(new ui::DefaultThemeProvider);
   if (params.type == InitParams::TYPE_MENU) {
     is_mouse_button_pressed_ =