Add MSAA and non-aa modes to GrFillRRect Op

Adds a non-aa mode and an MSAA mode that uses the sample mask. Also
adds a new cap to decide whether we prefer this new sample mask Op for
large round rects, or whether it's faster to just continue drawing
them as paths like before.

Bug: skia:
Change-Id: Ic344ace26e7889c312c3040ad345b4d9a717f96d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/204135
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
10 files changed