This is an unrelated code cleanup. Previously we would only init these
member variables in the gl::State initialization code.

Bug: angleproject:3611
Change-Id: I3aa34958ce5b00542d45ef63e0b32010b2eb3220
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1902188Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>