Add kAccessibilityFocusFallsbackToWidget property

ui/views/bubble/bubble_dialog_delegate.cc

Index: ui/views/bubble/bubble_dialog_delegate.cc
diff --git a/ui/views/bubble/bubble_dialog_delegate.cc b/ui/views/bubble/bubble_dialog_delegate.cc
index dd1b2eea6420fdfea199431f4fce0622fe791bf3..c17de9779d429cded14157784ea195a5145c4bea 100644
--- a/ui/views/bubble/bubble_dialog_delegate.cc
+++ b/ui/views/bubble/bubble_dialog_delegate.cc
@@ -14,6 +14,7 @@
 #include "ui/views/bubble/bubble_frame_view.h"
 #include "ui/views/focus/view_storage.h"
 #include "ui/views/layout/layout_constants.h"
+#include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_observer.h"
 #include "ui/views/window/dialog_client_view.h"
@@ -42,6 +43,11 @@ Widget* CreateBubbleWidget(BubbleDialogDelegateView* bubble) {
                                   : Widget::InitParams::ACTIVATABLE_NO;
   bubble->OnBeforeBubbleWidgetInit(&bubble_params, bubble_widget);
   bubble_widget->Init(bubble_params);
+
+  View* root_view = bubble_widget->GetRootView();
+  if (root_view != nullptr)
+    root_view->SetFocusBehavior(View::FocusBehavior::ACCESSIBLE_ONLY);
+
   if (bubble_params.parent)
     bubble_widget->StackAbove(bubble_params.parent);
   return bubble_widget;