Bug 255439

In Document::updateResizeObservations we throw an error if we exceed some limit for the number of times we loop processing ResizeObserver notifications.  This uses getParserLocation to get the location to use in the error, which returns the empty string if parsing the document has finished.  I think we should just use the document URL.  When we pass in the empty string to reportException, we end up censoring the error message as "Script error." because we think the error came from a different origin, and the "ResizeObserver loop completed with undelivered notifications." message gets lost.