Revert 149589 "Set a bit on Custom Elements on creation to simplify wrapping"

Source/core/dom/CustomElementRegistry.h

Index: Source/core/dom/CustomElementRegistry.h
diff --git a/Source/core/dom/CustomElementRegistry.h b/Source/core/dom/CustomElementRegistry.h
index 86869d94433fd287360eab00667df061bb7403c6..77ffd405f88c0815ae97808021f80e62a479c871 100644
--- a/Source/core/dom/CustomElementRegistry.h
+++ b/Source/core/dom/CustomElementRegistry.h
@@ -79,6 +79,9 @@ public:
 
     PassRefPtr<CustomElementConstructor> registerElement(WebCore::ScriptState*, const AtomicString& name, const Dictionary& options, ExceptionCode&);
 
+    // FIXME: findFor is dangerous since it consults the "is"
+    // attribute; that should only be consulted at element creation
+    // time.
     PassRefPtr<CustomElementDefinition> findFor(Element*) const;
     PassRefPtr<CustomElementDefinition> findAndCheckNamespace(const AtomicString& type, const AtomicString& namespaceURI) const;