SaveLayerRec::fClipMask -> raw pointer

Use raw pointers for optional clip mask plumbing, to match the backdrop
API.

Change-Id: I7eb0ee5896faf34cc05789ba0703f35a4ab6a4f2
Reviewed-on: https://skia-review.googlesource.com/14901
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
14 files changed