Move clear-as-draw caps into GrCaps

Bug: skia:
Change-Id: Ib029f337f5e61366e2550e77dc99310b44d03f84
Reviewed-on: https://skia-review.googlesource.com/c/182970
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
9 files changed