This removes unnecessary memory allocations.

BUG=angleproject:2267
TEST=angle_unittests

Change-Id: Ide575ea19ab2f8e9fc93092490f1352efa6024a3
Reviewed-on: https://chromium-review.googlesource.com/817415
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>