Pass the SubRun storage to draw to be counted in the op

This is a CL to make the APIs for SubRuns more Blob/Slug
agnostic. The aim is to make the process* code for Blobs and
Slug the same.

Change-Id: I087da97ea4c56e5d37619a43b2aa2458bc58914c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/542648
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>
4 files changed