Update DDL testing harness to support drawing DDL w/ integer offsets

This isn't hooked up anywhere but breaks up the omnibus CL.

Change-Id: I15c200e57450e7cc8ee95a3f7969926d0eb8487f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/333129
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
9 files changed