Maths was wonky, causing the blocks to go back one on a whole integer.
Change-Id: I1f7d49c1d1b12050dd48b2090dbeff9d4a1c6c38
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/133600
Auto-Submit: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>