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