Remove almost all clients of isHTMLElement

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

 {% from "macros.tmpl" import license %}
 {{ license() }}
 
 #include "config.h"
 #include "{{namespace}}ElementFactory.h"
 
 #include "{{namespace}}Names.h"
 {% for tag in tags|sort %}
 #include "core/{{namespace|lower}}/{{tag.interface}}.h"
 {% endfor %}
@@ skipping 53 matching lines @@
     {% for tag in tags|sort if not tag.noConstructor %}
     {% filter enable_conditional(tag.Conditional) %}
         { {{tag|symbol}}Tag, {{tag|symbol}}Constructor },
     {% endfilter %}
     {% endfor %}
     };
     for (size_t i = 0; i < WTF_ARRAY_LENGTH(data); i++)
         g_constructors->set(data[i].tag.localName(), data[i].func);
 }
 
-PassRefPtr<{{namespace}}Element> {{namespace}}ElementFactory::create{{namespace}}Element(
+PassRefPtr<Element> {{namespace}}ElementFactory::createElement(
     const AtomicString& localName,
     Document& document,
     bool createdByParser)
 {
     if (!g_constructors)
         create{{namespace}}FunctionMap();
     if (ConstructorFunction function = g_constructors->get(localName))
         return function(document, createdByParser);
 
-    if (CustomElement::isValidName(localName)) {
-        RefPtr<Element> element = document.registrationContext().createCustomTagElement(document, QualifiedName(localName));
-        ASSERT_WITH_SECURITY_IMPLICATION(element->is{{namespace}}Element());
-        return static_pointer_cast<{{namespace}}Element>(element.release());
-    }
+    if (CustomElement::isValidName(localName))
+        return document.registrationContext().createCustomTagElement(document, QualifiedName(localName));
 
     return {{fallback_interface}}::create(QualifiedName(localName), document);
 }
 
 } // namespace blink