Replace phantomjs for closure_js_test

I find that phantomjs renders closure_js_test rather limited in terms of web apis, it's hard to use, and the error messages aren't very good.

Is there any appetite for replacing phantomjs with some sort of headless chrome or other browser? Has anyone started on such work?

For those interested in seeing phantomjs go away, what alternative(s) would you like to see?

Start by examining the closure_js_test entry point and how it invokes PhantomJS. Research suitable headless-browser alternatives and their web API and error-reporting support; done would require an agreed replacement and a migrated test path, but the issue does not specify either.

Written by the indexing model from the issue text.