Implement Custom Elements 'extends' option.

Source/core/dom/CustomElementRegistry.cpp

 /*
  * Copyright (C) 2012 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 60 matching lines @@
     if (!constructorBuilder->isFeatureAllowed()) {
         CustomElementException::throwException(CustomElementException::CannotRegisterFromExtension, type, es);
         return 0;
     }
 
     if (!CustomElement::isValidName(type, validNames)) {
         CustomElementException::throwException(CustomElementException::InvalidName, type, es);
         return 0;
     }
 
-    if (!constructorBuilder->validateOptions(type, es))
+    QualifiedName tagName = nullQName();
+    if (!constructorBuilder->validateOptions(type, tagName, es))
         return 0;
 
-    QualifiedName tagName = nullQName();
-    if (!constructorBuilder->findTagName(type, tagName)) {
-        CustomElementException::throwException(CustomElementException::PrototypeDoesNotExtendHTMLElementSVGElementNamespace, type, es);
-        return 0;
-    }
     ASSERT(tagName.namespaceURI() == HTMLNames::xhtmlNamespaceURI || tagName.namespaceURI() == SVGNames::svgNamespaceURI);
 
+    // FIXME: This should be done earlier in validateOptions.
     if (m_registeredTypeNames.contains(type)) {
         CustomElementException::throwException(CustomElementException::TypeAlreadyRegistered, type, es);
         return 0;
     }
 
     ASSERT(!observer.registrationContextWentAway());
 
     RefPtr<CustomElementLifecycleCallbacks> lifecycleCallbacks = constructorBuilder->createCallbacks();
 
     // Consulting the constructor builder could execute script and
@@ skipping 19 matching lines @@
 
     return definition.get();
 }
 
 CustomElementDefinition* CustomElementRegistry::find(const CustomElementDescriptor& descriptor) const
 {
     return m_definitions.get(descriptor);
 }
 
 } // namespace WebCore