mFileSpec = prefsFile; rv = SavePrefFile();
nsresult nsPref::useDefaultPrefFile()//----------------------------------------------------------------------------------------{    nsIFileSpec* prefsFile = NS_LocateFileOrDirectory(nsSpecialFileSpec::App_PreferencesFile50);    nsresult rv = NS_OK;    if (!prefsFile)    {	    // There is no locator component. Or perhaps there is a locator, but the	    // locator couldn't find where to put it. So put it in the cwd (NB, viewer comes here.)        // #include nsIComponentManager.h        rv = nsComponentManager::CreateInstance(        	(const char*)NS_FILESPEC_PROGID,        	(nsISupports*)nsnull,        	(const nsID&)nsIFileSpec::GetIID(),        	(void**)&prefsFile);        NS_ASSERTION(NS_SUCCEEDED(rv), "ERROR: Could not make a file spec.");	    if (!prefsFile)	    	return NS_ERROR_FAILURE;	    prefsFile->SetUnixStyleFilePath("default_prefs.js"); // in default working directory.    }    if (Exists(prefsFile))        return ReadUserPrefsFrom(prefsFile);    return rv;} // nsPref::useDefaultPrefFile