Add test for context lost issue with Figma on certain Intel GPUs

In Chromium bug https://crbug.com/1253941 a problem was identified with a [Figma](https://www.figma.com/) drawing that was causing a WebGL context loss upon loading.

A root cause still hasn't been identified, but a later driver version fixed the problem. It's important that this be distilled down and a test added to the WebGL conformance suite in order to prevent serious regressions like this one from happening again, as Intel, and other GPU vendors, are running the WebGL conformance tests in-house.

Start by reviewing Chromium bug 1253941 and the WebGL conformance suite to determine how the Figma drawing can be distilled into a reproducible test. Done means the distilled case is included in the suite and covers the context-loss regression described for affected Intel GPUs.

Written by the indexing model from the issue text.