Move some tests from web-platform-tests

[foolip]

This is the mirror issue of web-platform-tests/wpt#8044, to track getting those tests into this repo.

[kenrussell]

Pull requests welcome. These tests seem pretty small, and they could be easily merged into existing tests like conformance/buffers/buffer-data-and-buffer-sub-data.html and conformance/extensions/webgl-compressed-texture-s3tc.html .

[foolip]

I labeled the wpt issue as good first issue, maybe someone will come along.