freeze happens after repetitive enter & exit full screen mode

Bug: angleproject:3431
Change-Id: Iea4cd75dc30cd17e53c0a7f1174e39b24d878d4b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1599617Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>