script problem

With gecko 1.8 I used the following code

    nsCOMPtr<nsIScriptGlobalObjectOwner>
theGlobalObjectOwner(do_GetInterface(mWebBrowser));
    Trace::write(deep_Trace,"WebBrowserChrome::executeScript");

    if (theGlobalObjectOwner)
    {
        nsIScriptGlobalObject* theGlobalObject;
        theGlobalObject=theGlobalObjectOwner-
>GetScriptGlobalObject(); // NOW thGlobalObject is NULL

		if (theGlobalObject)
		{
			nsIScriptContext* theScriptContext = theGlobalObject->GetContext();

			UnicodeString unicodeScript = UnicodeString::fromLatin1(aScript);
			nsAutoString script((wchar_t*)unicodeScript.data());

			//todo: fuite mémoire (memory leak)
			PRBool        IsUndefined;
			Trace::write(deep_Trace,"WebBrowserChrome
executeScript(%s)",aScript.c_str());

			theScriptContext->EvaluateString(script,
											 nsnull,
											 nsnull,
											 "",
											 1,
											 nsnull,
											 nsnull,
											 &IsUndefined);
		}
		else
		{
			return false;
			}
    }

    return true;
}


But with 1.9.2.23  theGlobalObject returned  by theGlobalObjectOwner-
>GetScriptGlobalObject();  is null

How can I get  a valid nsScriptGlobalObject.. Did the architecture of
the classes change ?

Is there a documentation about the architecture. I have
http://doxygen.db48x.net/mozilla-full/html/index.html, but it's very
deep!!!!

Thank's a lot for your responses

philippe