This apparently can save on memory usage in the allocator.

Reported by penghuang@chromium.org.

Bug: angleproject:4685
Change-Id: I6f29280e3fe16f3388c4f8412e0acb09d7f16e58
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2216714Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>