Simplify GrDefaultPathRenderer a tiny bit

This is far less compelling than https://codereview.chromium.org/2135053002/ (Simplify MSAA path renderer) but is probably still worth it.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2135853003

Review-Url: https://codereview.chromium.org/2135853003
1 file changed