Switch from size_t to uint32_t to represent constraints better.

TBR=mtklein@google.com

Change-Id: Ib7400f2a3e2af0d8976998e5857c4d2c9cb6dbd0
Reviewed-on: https://skia-review.googlesource.com/7614
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed