Add a "conservative raster" flag for GrFillRectOp

Adds the ability to fill a rect with conservative raster enabled, and
fixes a bug in the gpu tessellation atlas where there were artifacts
from mixed samples.

Change-Id: Ic0b4f2059129ac238fdcb08d43896fc2b9e50211
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/269989
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
5 files changed