Includes test specs for Linux/Mac/Win7/Win10. Android is left out
for a second pass to keep the changes a bit simpler.

Bug: angleproject:5114
Change-Id: I94e7f7f273073f85488ec982e89b4b68f45627ac
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2805371
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>