Add convenience methods to CFG builder.

This doesn't change the meaning or intent at all, just makes the code
easier to read.

Change-Id: I998498de8fba625d86eadc2fba119c29a1e1d29a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/318202
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed