Specify DrawList as using a z test of "GREATER"

A test of GREATER, as opposed to GEQUAL, allows us to avoid double
blends during stroking.

Change-Id: I1d39b54416934ee354146fe42c58299f00f7a6e9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/453616
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
1 file changed