CErrorHandler has been refactored to respect errorAction on AJAX request.
Issue #2753 has been added to CHANGELOG
CErrorHandler::errorAction via AJAX has been added to UPGRADE
Unnecessary comment at CErrorHandler::render() has been removed.
Merge pull request #2830 from klimov-paul/2753-error-action-with-ajax

Fix #2753 CErrorHandler::errorAction ignored at PHP error + AJAX request