This Context could already be deleted from another thread. Better to
use save/load with the current thread.

Bug: angleproject:2464
Change-Id: Id7879a53bdfb7d1c86b09bb3e779a87afdefa873
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1756086Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>