Implement :valid and :invalid pseudoclass for <form>

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 461a29ae20a503629183fcd684accf22636146eb..fae5c8add19ef8353e997f2a26a7b56f1a35edcd 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -429,7 +429,7 @@ public:
     virtual bool isRequiredFormControl() const { return false; }
     virtual bool isDefaultButtonForForm() const { return false; }
     virtual bool willValidate() const { return false; }
-    virtual bool isValidFormControlElement() { return false; }
+    virtual bool isValidElement() { return false; }
     virtual bool isInRange() const { return false; }
     virtual bool isOutOfRange() const { return false; }
     virtual bool isClearButtonElement() const { return false; }