Count element name validity per DOM versus HTML parsing.

third_party/WebKit/Source/bindings/core/v8/V0CustomElementConstructorBuilder.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 325 matching lines @@
       V8StringResource<>, tag_name,
       V8PrivateProperty::GetCustomElementTagName(isolate).GetOrEmpty(data));
   v8::Local<v8::Value> maybe_type =
       V8PrivateProperty::GetCustomElementType(isolate).GetOrEmpty(data);
   TOSTRING_VOID(V8StringResource<>, type, maybe_type);
 
   ExceptionState exception_state(isolate, ExceptionState::kConstructionContext,
                                  "CustomElement");
   V0CustomElementProcessingStack::CallbackDeliveryScope delivery_scope;
   Element* element = document->createElementNS(
-      namespace_uri, tag_name,
+      nullptr, namespace_uri, tag_name,
       StringOrDictionary::fromString(maybe_type->IsNull() ? g_null_atom : type),
       exception_state);
   if (element) {
     UseCounter::Count(document, UseCounter::kV0CustomElementsConstruct);
   }
   V8SetReturnValueFast(info, element, document);
 }
 
 }  // namespace blink