Hide (unused) SkDrawLooper

Bug: skia:8672
Change-Id: Ib8b614d94925b3cc7d02be422dbb7e96ea4c26b6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366338
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
18 files changed