Replace elementHasLegalLinkAttribute() helper with virtual function

Source/core/html/HTMLFrameElementBase.cpp

Index: Source/core/html/HTMLFrameElementBase.cpp
diff --git a/Source/core/html/HTMLFrameElementBase.cpp b/Source/core/html/HTMLFrameElementBase.cpp
index 31fb145078a2fa7d926bd421b5a0ffef6c06ea75..37b64ab10f67fb5bbde4f2ff90215927e55bdba5 100644
--- a/Source/core/html/HTMLFrameElementBase.cpp
+++ b/Source/core/html/HTMLFrameElementBase.cpp
@@ -204,6 +204,11 @@ bool HTMLFrameElementBase::isURLAttribute(const Attribute& attribute) const
         || HTMLFrameOwnerElement::isURLAttribute(attribute);
 }
 
+bool HTMLFrameElementBase::hasLegalLinkAttribute(const QualifiedName& name) const
+{
+    return name == hrefAttr || HTMLFrameOwnerElement::hasLegalLinkAttribute(name);
+}
+
 bool HTMLFrameElementBase::isHTMLContentAttribute(const Attribute& attribute) const
 {
     return attribute.name() == srcdocAttr || HTMLFrameOwnerElement::isHTMLContentAttribute(attribute);