Non-activated default buttons prevent implicit form submission.

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 155 matching lines @@
 }
 
 Node* HTMLFormElement::item(unsigned index)
 {
     return elements()->item(index);
 }
 
 void HTMLFormElement::submitImplicitly(Event* event, bool fromImplicitSubmissionTrigger)
 {
     int submissionTriggerCount = 0;
+    bool seenDefaultButton = false;
     for (unsigned i = 0; i < m_associatedElements.size(); ++i) {
         FormAssociatedElement* formAssociatedElement = m_associatedElements[i];
         if (!formAssociatedElement->isFormControlElement())
             continue;
         HTMLFormControlElement* control = toHTMLFormControlElement(formAssociatedElement);
-        if (control->isSuccessfulSubmitButton()) {
-            if (control->renderer()) {
-                control->dispatchSimulatedClick(event);
+        if (!seenDefaultButton && control->canBeSuccessfulSubmitButton()) {

[eseidel, 2013/11/14 16:40:32]

I think you mean couldBeSuccessful?
http://en.wikipedia.org/wiki/Subjunctive_mood since it's talking about something
uncertain in the future?

[sof, 2013/11/15 08:52:15]

Maybe the naming could be made clearer, it currently reflects the naming of the
InputType method. I could certainly follow up and rename this, if that's what we
want.

(Actually, I wanted to use isSubmitButton() here for closer correspondence to
spec, but its use is close to deprecated..and would have to be tweaked slightly
to admit image buttons.)

+            if (fromImplicitSubmissionTrigger)
+                seenDefaultButton = true;
+            if (control->isSuccessfulSubmitButton()) {
+                if (control->renderer()) {
+                    control->dispatchSimulatedClick(event);
+                    return;
+                }
+            } else if (fromImplicitSubmissionTrigger) {
+                // Default (submit) button is not activated; no implicit submission.
                 return;
             }
-        } else if (control->canTriggerImplicitSubmission())
+        } else if (control->canTriggerImplicitSubmission()) {
             ++submissionTriggerCount;
+        }
     }
     if (fromImplicitSubmissionTrigger && submissionTriggerCount == 1)
         prepareForSubmission(event);
 }
 
 // FIXME: Consolidate this and similar code in FormSubmission.cpp.
 static inline HTMLFormControlElement* submitElementFromEvent(const Event* event)
 {
     for (Node* node = event->target()->toNode(); node; node = node->parentOrShadowHostNode()) {
         if (node->isElementNode() && toElement(node)->isFormControlElement())
@@ skipping 601 matching lines @@
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace