Implement Custom Elements inserted and removed callbacks.

Source/bindings/v8/CustomElementConstructorBuilder.h

 /*
  * 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 60 matching lines @@
     void didRegisterDefinition(CustomElementDefinition*, const HashSet<Element*>& upgradeCandidates) const;
 
     // This method collects a return value for the bindings. It is
     // safe to call this method even if the builder failed; it will
     // return an empty value.
     ScriptValue bindingsReturnValue() const;
 
 private:
     bool hasValidPrototypeChainFor(WrapperTypeInfo*) const;
     bool prototypeIsValid() const;
+    v8::Handle<v8::Function> retrieveCallback(const char* name) const;
 
     v8::Handle<v8::Context> m_context;
     const Dictionary* m_options;
     v8::Handle<v8::Object> m_prototype;
     AtomicString m_namespaceURI;
     v8::Handle<v8::Function> m_constructor;
 };
 
 }
 
 #endif // CustomElementConstructorBuilder_h