/**
* Dumb window.onerror handler which forwards the errors via mw.track.
*
+ * @param {string} errorMessage
+ * @param {string} url
+ * @param {number} lineNumber
+ * @param {number} [columnNumber]
+ * @param {Error|Mixed} [errorObject]
+ * @return {boolean} True to prevent the default action
* @fires global_error
*/
window.onerror = function ( errorMessage, url, lineNumber, columnNumber, errorObject ) {