nsProperties::HasProperty(const char* prop, nsISupports* expectedValue)
nsPersistentProperties::HasProperty(const char* prop, nsISupports* value)
nsProperties::HasProperty(const char* prop, nsISupports* expectedValue){    nsISupports* value;    nsresult rv = GetProperty(prop, &value);    if (NS_FAILED(rv)) return NS_COMFALSE;    rv = (value == expectedValue) ? NS_OK : NS_COMFALSE;    NS_IF_RELEASE(value);    return rv;}