Handle stroked single line special case in Ganesh

This CL roughly halves the time spent on the captured stroked lines skp.
On my Linux desktop it boosts the external benchmark from 2618 to 5007.

This is a companion to: https://codereview.chromium.org/2019193002/ (Add new GM to exercise stroked line special case)

The idea is to land the GM first so any regressions are visible.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2023693002

Review-Url: https://codereview.chromium.org/2023693002
4 files changed