<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 fe954d12828961f72141cf36dfe14433342f1a3a..ce8ec010db37ae2adff83a5cd4270dbc8ef6dbd0 100644
--- a/Source/core/html/HTMLFormElement.cpp
+++ b/Source/core/html/HTMLFormElement.cpp
@@ -729,7 +729,7 @@ bool HTMLFormElement::checkInvalidControlsAndCollectUnhandled(WillBeHeapVector<R
     for (unsigned i = 0; i < elements.size(); ++i) {
         if (elements[i]->form() == this && elements[i]->isFormControlElement()) {
             HTMLFormControlElement* control = toHTMLFormControlElement(elements[i].get());
-            if (!control->checkValidity(unhandledInvalidControls, eventBehavior) && control->formOwner() == this) {
+            if (control->isSubmittableElement() && !control->checkValidity(unhandledInvalidControls, eventBehavior) && control->formOwner() == this) {
                 ++invalidControlsCount;
                 if (!unhandledInvalidControls && eventBehavior == CheckValidityDispatchNoEvent)
                     return true;