This converts
webgl_conformance_vulkan_passthrough_tests/texture-size.html to an
end2end test for ease of debugging.

Bug: chromium:1197905
Change-Id: If77dc30e81450b277c6a02d66c076b088d069498
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2821944
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>