Non-activated default buttons prevent implicit form submission.

Source/core/html/HTMLButtonElement.cpp

Index: Source/core/html/HTMLButtonElement.cpp
diff --git a/Source/core/html/HTMLButtonElement.cpp b/Source/core/html/HTMLButtonElement.cpp
index cebae34c182e2ce6f3a8c329496e02f2130b737a..a53422e6c16fac006308b0314355ec7b94e13562 100644
--- a/Source/core/html/HTMLButtonElement.cpp
+++ b/Source/core/html/HTMLButtonElement.cpp
@@ -159,11 +159,11 @@ bool HTMLButtonElement::willRespondToMouseClickEvents()
     return HTMLFormControlElement::willRespondToMouseClickEvents();
 }
 
-bool HTMLButtonElement::isSuccessfulSubmitButton() const
+bool HTMLButtonElement::canBeSuccessfulSubmitButton() const
 {
     // HTML spec says that buttons must have names to be considered successful.

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

Interesting that we're choosing to follow one bit of HTML5 here, but not
another.

[tkent, 2013/11/15 00:04:31]

It seems the WHATWG specification doesn't ask it.  We should remove the comment.

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

Done. I couldn't find any mention of this either (nor could others here remember
this being a constraint at some point.)

     // However, other browsers do not impose this constraint.
-    return m_type == SUBMIT && !isDisabledFormControl();
+    return m_type == SUBMIT;
 }
 
 bool HTMLButtonElement::isActivatedSubmit() const