begin to hide details of SkPathEffect

BUG=skia:

Change-Id: I155d2370ae894e6000b6a768d02cf06bf5b3de6e
Reviewed-on: https://skia-review.googlesource.com/8977
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
12 files changed