submit() in submit event handler should not contains a value of a submit button.

third_party/WebKit/Source/core/html/HTMLFormElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 48 matching lines @@
     void setEncoding(const AtomicString& value) { setEnctype(value); }
 
     bool shouldAutocomplete() const;
 
     void associate(FormAssociatedElement&);
     void disassociate(FormAssociatedElement&);
     void associate(HTMLImageElement&);
     void disassociate(HTMLImageElement&);
     void didAssociateByParser();
 
-    void prepareForSubmission(Event*);
+    void prepareForSubmission(Event*, HTMLFormControlElement* submitButton);
     void submitFromJavaScript();
     void reset();
 
     void setDemoted(bool);
 
     void submitImplicitly(Event*, bool fromImplicitSubmissionTrigger);
 
     String name() const;
 
     bool noValidate() const;
@@ skipping 32 matching lines @@
 
     void parseAttribute(const QualifiedName&, const AtomicString&, const AtomicString&) override;
     bool isURLAttribute(const Attribute&) const override;
     bool hasLegalLinkAttribute(const QualifiedName&) const override;
 
     bool shouldRegisterAsNamedItem() const override { return true; }
 
     void copyNonAttributePropertiesFromElement(const Element&) override;
 
     void submitDialog(FormSubmission*);
-    void submit(Event*, bool activateSubmitButton);
+    void submit(Event*, HTMLFormControlElement* submitButton);
 
     void scheduleFormSubmission(FormSubmission*);
 
     void collectAssociatedElements(Node& root, FormAssociatedElement::List&) const;
     void collectImageElements(Node& root, HeapVector<Member<HTMLImageElement>>&);
 
     // Returns true if the submission should proceed.
     bool validateInteractively();
 
     // Validates each of the controls, and stores controls of which 'invalid'
@@ skipping 30 matching lines @@
     bool m_hasElementsAssociatedByParser : 1;
     bool m_hasElementsAssociatedByFormAttribute : 1;
     bool m_didFinishParsingChildren : 1;
     bool m_isInResetFunction : 1;
     bool m_wasDemoted : 1;
 };
 
 } // namespace blink
 
 #endif // HTMLFormElement_h