Line drawing / clipping in deqp/functional/gles3/clipping.html fails on all Intel ChromeOS devices

It was recently discovered that some of the line drawing tests in the WebGL 2.0 conformance test [deqp/functional/gles3/clipping.html](https://github.com/KhronosGroup/WebGL/blob/main/sdk/tests/deqp/functional/gles3/clipping.html) fail on Intel GPUs on ChromeOS. Per the Chromium CL which suppressed these failures, https://chromium-review.googlesource.com/c/chromium/src/+/5180916 , it's effectively an off-by-one difference on whether a line going to a fractional screen coordinate fills the fragment at its end, or not. It appears to be caused by a difference in Intel's graphics driver compared to other GPUs. (Apologies, the linked Chromium bug is restricted-view.)

This failure also seems fairly minor - I personally doubt many WebGL applications would break if the rules in this area were relaxed.

Let's compare the current version of this test in Khronos' VK-GL-CTS with the ported WebGL 2.0 conformance test and see if the test has been updated in the intervening years. If so, let's apply those edits - maybe the test failure will be resolved. If not, let's consider loosening the test's requirements since this is a platform with many users and it seems unreasonable to deny WebGL 2.0 conformance for this one reason.

Start with deqp/functional/gles3/clipping.html and compare it with the current corresponding test in Khronos' VK-GL-CTS. Read Chromium CL 5180916 for the Intel ChromeOS failure context, then determine whether the tests differ and whether the existing requirement should be adjusted. Done means the comparison is resolved and the Intel ChromeOS conformance failure has a tested, maintainable outcome.

Written by the indexing model from the issue text.