Create ResourceProgressEvent, expose as Chromium API

Source/WebKit/chromium/public/WebDOMEvent.h

 /*
  * Copyright (C) 2010 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 94 matching lines @@
 
     template<typename T> const T toConst() const
     {
         T res;
         res.WebDOMEvent::assign(*this);
         return res;
     }
 
 protected:
     typedef WebCore::Event WebDOMEventPrivate;
+    // assign() assumes that the given WebCore::Event has already had a
+    // reference-count added by the caller. This WebDOMEvent takes ownership of
+    // that ref-count.
     void assign(WebDOMEventPrivate*);
+    void assign(const WTF::PassRefPtr<WebDOMEventPrivate>&);
     WebDOMEventPrivate* m_private;
 
     template<typename T> T* unwrap()
     {
         return static_cast<T*>(m_private);
     }
 
     template<typename T> const T* constUnwrap() const
     {
         return static_cast<const T*>(m_private);
     }
 };
 
 } // namespace WebKit
 
 #endif