GrTessellator: always rewind to edge top when splitting.

In some cases, a split edge may go out-of-order with a neighbouring edge
which has already been removed from the active edge list.

The only way to be sure is to always rewind to the edge top.
This may have performance implications for paths with many (hundreds) of
self-intersections. We'll have to watch the bots carefully.

Bug: 966274, 966364.
Change-Id: I5a1b7abe9baa7fc279cbf7d1dfa258dcdaa35f11
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/217637
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
2 files changed