Add variable offset support

Bug: skia:7970
Change-Id: I9dadf75f21e19ebe26f82643bcc47dd5794d8970
Reviewed-on: https://skia-review.googlesource.com/134421
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed