<fieldset> should be ignored in interactive validation

Source/core/html/HTMLFormElement.cpp

Index: Source/core/html/HTMLFormElement.cpp
diff --git a/Source/core/html/HTMLFormElement.cpp b/Source/core/html/HTMLFormElement.cpp
index f73c02b6a8c4bcf56f1622b0a995e25de8f978a2..6239225ab94e40e5766eeb145f16a2d043f4c924 100644
--- a/Source/core/html/HTMLFormElement.cpp
+++ b/Source/core/html/HTMLFormElement.cpp
@@ -303,7 +303,7 @@ bool HTMLFormElement::validateInteractively()
     if (document().frame()) {
         for (unsigned i = 0; i < unhandledInvalidControls.size(); ++i) {
             HTMLFormControlElement* unhandled = unhandledInvalidControls[i].get();
-            if (unhandled->isFocusable())
+            if (unhandled->isFocusable() || unhandled->formControlType() == "fieldset")

[tkent, 2015/06/25 06:16:45]

Here is not the correct place to check if it's <fieldset>.

The specification says fieldset is omitted in "statically validate the
constraints" step.
https://html.spec.whatwg.org/multipage/forms.html#statically-validate-the-con...
In our implementation, it's
HTMLFormElement::checkInvalidControlsAndCollectUnhandled().
We should add isSubmittableElement [1] to HTMLFormControlElement, and
checkInvalidControlsAndCollectUnhandled() should be:

HTMLFormControlElement* control = toHTMLFormControlElement(elements[i].get());
if (control->isSubmittableElement() &&
!control->checkValidity(unhandledInvalidControls, eventBehavior) &&
control->formOwner() == this) {
    ++invalidControlsCount;

[1] https://html.spec.whatwg.org/multipage/forms.html#category-submit

                 continue;
             String message("An invalid form control with name='%name' is not focusable.");
             message.replace("%name", unhandled->name());