Start with event_target in for loop to avoid GetEventTargeter crash.

ui/aura/window_event_dispatcher.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 "ui/aura/window_event_dispatcher.h"
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 437 matching lines @@
   if (event->IsLocatedEvent()) {
     ui::EventTarget* target = event_targeter_->FindTargetInRootWindow(
         window(), *event->AsLocatedEvent());
     if (target) {
       ConvertEventLocationToTarget(event_target, target, event);
       return target;
     }
   }
 
   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;
     if (ancestor == window())
       break;
   }
   ConvertEventLocationToTarget(event_target, ancestor_with_targeter, event);
   return ancestor_with_targeter;
 }
 
@@ skipping 447 matching lines @@
   }
 
   // This flag is set depending on the gestures recognized in the call above,
   // and needs to propagate with the forwarded event.
   event->set_may_cause_scrolling(orig_event.may_cause_scrolling());
 
   return PreDispatchLocatedEvent(target, event);
 }
 
 }  // namespace aura