[Fuchsia] Allow to use stub GL implementation

Now stub GL can be enabled with --use-gl=stub when using Scenic ozone
backend on Fuchsia. This allows to start using OOP-R with Vulkan before
we get ANGLE working on Fuchsia.

Bug: 962617
Change-Id: I19a1b8082a4238a116d6963a476fe92fa8ad5f05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1614622
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660719}
2 files changed