Use the two Custom Elements node bits to explicitly represent four states.

Source/core/dom/CustomElementRegistrationContext.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:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 127 matching lines @@
 
     if (HTMLNames::xhtmlNamespaceURI == tagName.namespaceURI()) {
         element = HTMLElement::create(tagName, document);
     } else if (SVGNames::svgNamespaceURI == tagName.namespaceURI()) {
         element = SVGElement::create(tagName, document);
     } else {
         // XML elements are not custom elements, so return early.
         return Element::create(tagName, document);
     }
 
-    element->setIsCustomElement();
     resolve(element.get());
     return element.release();
 }
 
 void ActiveRegistrationContext::didGiveTypeExtension(Element* element)
 {
     resolve(element);
 }
 
 void ActiveRegistrationContext::resolve(Element* element)
 {
-    ASSERT(element->isCustomElement());
-    ASSERT(!element->isUpgradedCustomElement());
     const CustomElementDescriptor& descriptor = describe(element);
     CustomElementDefinition* definition = m_registry.find(descriptor);
     if (definition)
         didResolveElement(definition, element);
     else
         didCreateUnresolvedElement(descriptor, element);
 }
 
 void ActiveRegistrationContext::didResolveElement(CustomElementDefinition* definition, Element* element)
 {
+    element->setCustomElementState(Element::Defined);
     CustomElementCallbackScheduler::scheduleCreatedCallback(definition->callbacks(), element);
 }
 
 void ActiveRegistrationContext::didCreateUnresolvedElement(const CustomElementDescriptor& descriptor, Element* element)
 {
+    element->setCustomElementState(Element::UpgradeCandidate);
     m_candidates.add(descriptor, element);
 }
 
 CustomElementDefinition* ActiveRegistrationContext::definitionFor(Element* element) const
 {
+    ASSERT(element->customElementState() == Element::Defined || element->customElementState() == Element::Upgraded);
     ASSERT(element->document()->registrationContext() == this);
     const CustomElementDescriptor& descriptor = describe(element);
     return m_registry.find(descriptor);
 }
 
 void ActiveRegistrationContext::customElementAttributeDidChange(Element* element, const AtomicString& name, const AtomicString& oldValue, const AtomicString& newValue)
 {
-    ASSERT(element->isUpgradedCustomElement());
+    ASSERT(element->customElementState() == Element::Upgraded);
     CustomElementDefinition* definition = definitionFor(element);
     CustomElementCallbackScheduler::scheduleAttributeChangedCallback(definition->callbacks(), element, name, oldValue, newValue);
 }
 
 void ActiveRegistrationContext::customElementDidEnterDocument(Element* element)
 {
-    ASSERT(element->isUpgradedCustomElement());
+    ASSERT(element->customElementState() == Element::Upgraded);
     CustomElementDefinition* definition = definitionFor(element);
     CustomElementCallbackScheduler::scheduleEnteredDocumentCallback(definition->callbacks(), element);
 }
 
 void ActiveRegistrationContext::customElementDidLeaveDocument(Element* element)
 {
-    ASSERT(element->isUpgradedCustomElement());
+    ASSERT(element->customElementState() == Element::Upgraded);
     CustomElementDefinition* definition = definitionFor(element);
     CustomElementCallbackScheduler::scheduleLeftDocumentCallback(definition->callbacks(), element);
 }
 
 void ActiveRegistrationContext::customElementIsBeingDestroyed(Element* element)
 {
     m_candidates.remove(element);
     CustomElementRegistrationContext::customElementIsBeingDestroyed(element);
 }
 
@@ skipping 25 matching lines @@
     return Document::isValidName(name.string());
 }
 
 bool CustomElementRegistrationContext::isCustomTagName(const AtomicString& localName)
 {
     return isValidTypeName(localName);
 }
 
 CustomElementDescriptor CustomElementRegistrationContext::describe(Element* element)
 {
-    ASSERT(element->isCustomElement());
-
     // If an element has a custom tag name it takes precedence over
     // the "is" attribute (if any).
     const AtomicString& type = isCustomTagName(element->localName())
         ? element->localName()
         : typeExtension(element);
 
     return CustomElementDescriptor(type, element->namespaceURI(), element->localName());
 }
 
 void CustomElementRegistrationContext::setIsAttributeAndTypeExtension(Element* element, const AtomicString& type)
 {
     ASSERT(element);
     ASSERT(!type.isEmpty());
     element->setAttribute(HTMLNames::isAttr, type);
     setTypeExtension(element, type);
 }
 
 void CustomElementRegistrationContext::setTypeExtension(Element* element, const AtomicString& type)
 {
     if (!element->isHTMLElement() && !element->isSVGElement())
         return;
 
     if (isCustomTagName(element->localName()))
         return; // custom tags take precedence over type extensions
 
     TypeExtensionMap::AddResult result = typeExtensionMap()->add(element, type);
     ASSERT(result.isNewEntry); // Type extensions should only be set once
-    element->setIsCustomElement();
     element->document()->registrationContext()->didGiveTypeExtension(element);
 }
 
 void CustomElementRegistrationContext::customElementIsBeingDestroyed(Element* element)
 {
     ASSERT(element->isCustomElement());
     typeExtensionMap()->remove(element);
 }
 
 const AtomicString& CustomElementRegistrationContext::typeExtension(Element* element)
 {
     TypeExtensionMap::const_iterator it = typeExtensionMap()->find(element);
     ASSERT(it != typeExtensionMap()->end());
     return it->value;
 }
 
 CustomElementRegistrationContext::TypeExtensionMap* CustomElementRegistrationContext::typeExtensionMap()
 {
     DEFINE_STATIC_LOCAL(TypeExtensionMap, typeExtensionMap, ());
     return &typeExtensionMap;
 }
 
 } // namespace WebCore