Remove almost all clients of isHTMLElement

sky/engine/build/scripts/templates/ElementFactory.h.tmpl

 {% from "macros.tmpl" import license %}
 {{ license() }}
 
 #ifndef {{namespace}}ElementFactory_h
 #define {{namespace}}ElementFactory_h
 
 #include "sky/engine/wtf/Forward.h"
 #include "sky/engine/wtf/PassRefPtr.h"
 
 namespace blink {
 
 class Document;
-class {{namespace}}Element;
+class Element;
 
 class {{namespace}}ElementFactory {
 public:
-    static PassRefPtr<{{namespace}}Element> create{{namespace}}Element(
+    static PassRefPtr<Element> createElement(
         const AtomicString& localName,
         Document&,
         bool createdByParser = true);
 };
 
 } // namespace blink
 
 #endif