This is a tracking issue for the project to improve the performance of sites that load parser blocking scripts using document.write.
These scripts are a major performance killer, especially on poor networks. Additionally, because they are parser blocking, they often postpone sending out requests for other dynamic content on the page. This causes under utilization of the network.
There are a number of small subprojects that are working on targeting specific wins regarding document.write.
Comment 1 by csharrison@chromium.org
, Mar 11 2016