Start with event_target in for loop to avoid GetEventTargeter crash.

ui/aura/window_event_dispatcher.cc

Index: ui/aura/window_event_dispatcher.cc
diff --git a/ui/aura/window_event_dispatcher.cc b/ui/aura/window_event_dispatcher.cc
index 02885e50c5cb50725468ce1e7e828f6835c51467..78ecee4d4604dcd3bc4fbde6f6c77c4b65b654e4 100644
--- a/ui/aura/window_event_dispatcher.cc
+++ b/ui/aura/window_event_dispatcher.cc
@@ -455,7 +455,7 @@ ui::EventTarget* WindowEventDispatcher::GetRootForEvent(ui::Event* event) {
   }
 
   ui::EventTarget* ancestor_with_targeter = event_target;
-  for (ui::EventTarget* ancestor = event_target->GetParentTarget(); ancestor;
+  for (ui::EventTarget* ancestor = event_target; ancestor;
        ancestor = ancestor->GetParentTarget()) {
     if (ancestor->GetEventTargeter())
       ancestor_with_targeter = ancestor;