This patch factors the CommandAllocator, CommandIterator, and error
handling out of CommandEncoderBase so it can later be used by the
RenderBundleEncoder.
Bug: dawn:154
Change-Id: Ia4f8c3ce7f432f0887b619bd8090aa9bec7330fc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9181
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Austin Eng