We were using repeated code patterns in several places.

Bug: angleproject:5736
Change-Id: I206783dd792c3b0f9d38027235445ec600a60d88
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2773320Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>