This extension is made core in GLES3.2. This CL adds the necessary
entry points to the frontend.

Bug: angleproject:3584
Change-Id: Icaaa0b298898f3360819966a7f67b5feaf05124b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2215305
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>