GrTessellator: fix for even/odd fill type and path holes.

When extracting contours for the even/odd fill type, connected holes
in the interior of a shape don't get rendered correctly.

The fix is to extract the subcontours separately from the outer contour.
To do this, we abort contour extraction the first time we re-encounter
the starting vertex.  This causes the hole to be extracted as a
separate contour.

Bug: 908646
Change-Id: I047b77c74605987c40c12a228fd2898c9aa74e55
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/220776
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
3 files changed