improved performance of parsing SkSLLayout flags

BUG=skia:

Change-Id: Ib0e1393fb44f5f934ad2f88fed638ef7a0fa7393
Reviewed-on: https://skia-review.googlesource.com/8463
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
2 files changed