Tack on ret instructions to each SkSplicer stage.

This is just a warm up refactor to make the existing stages more
amenable to running in place without splicing.  Hopefully the driver
interpreter loop for that will be my next CL.

Change-Id: Ie76868b59af8ff3a10e2cd64f03c3f8d8a5031dd
Reviewed-on: https://skia-review.googlesource.com/8142
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
3 files changed