Use bulk SkPoint serialization API for DirectMaskSubRun

Use the bulk SkPoint serialization routines in the DirectMaskSubRun.
I tried doing all the SubRuns at once in a previous CL, but that
failed. I'm going slowly, and converting one SubRun at a time.

Change-Id: I36f343590a96d918f768575b198ddb93a1c059d5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/564057
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
1 file changed