Internalize vertexStride calculation to SubRun

Change-Id: I58e5c192ae81b4464b74e02655a43008da9e36f4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261441
Commit-Queue: Herb Derby <herb@google.com>
Auto-Submit: Herb Derby <herb@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed