Don't delay submit in onsubmit event handler

Source/core/html/HTMLFormElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 285 matching lines @@
     if (!validateInteractively(event)) {
         m_isSubmittingOrPreparingForSubmission = false;
         return false;
     }
 
     StringPairVector controlNamesAndValues;
     getTextFieldValues(controlNamesAndValues);
     RefPtr<FormState> formState = FormState::create(this, controlNamesAndValues, &document(), NotSubmittedByJavaScript);
     frame->loader().client()->dispatchWillSendSubmitEvent(formState.release());
 
+    // Set flag before submission as dispatchEvent could trigger another event
+    m_isSubmittingOrPreparingForSubmission = false;
+
     if (dispatchEvent(Event::createCancelableBubble(EventTypeNames::submit)))
         m_shouldSubmit = true;
 
-    m_isSubmittingOrPreparingForSubmission = false;
-
     if (m_shouldSubmit)
         submit(event, true, true, NotSubmittedByJavaScript);
 
     return m_shouldSubmit;
 }
 
 void HTMLFormElement::submit()
 {
     submit(0, false, true, NotSubmittedByJavaScript);
 }
@@ skipping 496 matching lines @@
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace