Add Dictionary get() method for AtomicString values and use it

Source/bindings/v8/CustomElementConstructorBuilder.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 70 matching lines @@
             return false;
         }
         m_prototype = prototypeScriptValue.v8Value().As<v8::Object>();
     } else {
         m_prototype = v8::Object::New(m_context->GetIsolate());
         v8::Local<v8::Object> basePrototype = V8PerContextData::from(m_context)->prototypeForType(&V8HTMLElement::wrapperTypeInfo);
         if (!basePrototype.IsEmpty())
             m_prototype->SetPrototype(basePrototype);
     }
 
-    String extends;
+    AtomicString extends;
     bool extendsProvidedAndNonNull = m_options->get("extends", extends);
 
     if (!V8PerContextData::from(m_context)) {
         // FIXME: This should generate an InvalidContext exception at a later point.
         CustomElementException::throwException(CustomElementException::ContextDestroyedCheckingPrototype, type, exceptionState);
         return false;
     }
 
     AtomicString namespaceURI = HTMLNames::xhtmlNamespaceURI;
     if (hasValidPrototypeChainFor(&V8SVGElement::wrapperTypeInfo))
         namespaceURI = SVGNames::svgNamespaceURI;
 
     AtomicString localName;
 
     if (extendsProvidedAndNonNull) {
         localName = extends.lower();

[Inactive, 2013/12/31 15:43:46]

String -> AtomicString conversion if extends is not an AtomicString.

 
         if (!Document::isValidName(localName)) {
             CustomElementException::throwException(CustomElementException::ExtendsIsInvalidName, type, exceptionState);
             return false;
         }
         if (CustomElement::isValidName(localName)) {
             CustomElementException::throwException(CustomElementException::ExtendsIsCustomElementName, type, exceptionState);
             return false;
         }
     } else {
@@ skipping 160 matching lines @@
 
     ExceptionState exceptionState(ExceptionState::ConstructionContext, "CustomElement", info.Holder(), info.GetIsolate());
     CustomElementCallbackDispatcher::CallbackDeliveryScope deliveryScope;
     RefPtr<Element> element = document->createElementNS(namespaceURI, tagName, maybeType->IsNull() ? nullAtom : type, exceptionState);
     if (exceptionState.throwIfNeeded())
         return;
     v8SetReturnValueFast(info, element.release(), document);
 }
 
 } // namespace WebCore