function sassLoadedViaNetwork(error, statusCode, headers, content)
        {
            if (error || statusCode >= 400) {
                console.error("Could not load content for " + sassURL + " : " + (error || ("HTTP status code: " + statusCode)));
                return;
            }
            var lastModified = this._checkLastModified(headers, sassURL);
            if (!lastModified)
                return;
            metadataReceived.call(this, lastModified);
        }
@param {?Protocol.Error} error
@param {number} statusCode
@param {!NetworkAgent.Headers} headers
@param {string} content
@this {WebInspector.SASSSourceMapping}