ES3 parsing compatibility for upstream in: https://github.com/hartman/vega/tree/jshint

Merged with https://github.com/nyurik/vega (this is our Vega fork). Submitted to upstream.

Change 210008 had a related patch set uploaded (by Yurik):
Bumped Vega to 1.5.3

https://gerrit.wikimedia.org/r/210008

Even though I merged the patch, I am still having doubts if we should do this if IE8 does not support canvases. Should we simply wrap around it, checking if canvases are supported, and keep the syntax cleaner (ES5)?

Upon further thinking, I think it would be a bad idea to introduce ES3-compatible code here - makes it too ugly. Instead, we should solve this with the conditional IMG fallback loading, e.g. detect canvas support and use the <img> tag if not. The fix should also prevent vega/d3 lib loading.

Change 210008 abandoned by Yurik:
Bumped Vega to 1.5.3

Reason:
per https://phabricator.wikimedia.org/T98689#1275665 - not a good approach

https://gerrit.wikimedia.org/r/210008

Well, the problem is that without the ES3 compatibility, you cannot DELIVER it to an IE8 client (it's a parsing error, not an execution error). That means that you need to do client side module loading, which MIGHT be a good idea, fore reasons stated in T98704

For execution on IE8, you would need an s5-shim and a canvas polyfill.

Since we are switching to <img> for everyone except when editing, see 209823, this issue should be solved for non-editing case.

Do we want to keep this issue, since now IE8 is no longer supported as grade A?