GrTessellator: handle collinear final vertex.

If the last vertex in a contour is collinear with its neighbours,
remove it (this edge case was missing). Otherwise, the simplify step
may try to split it indefinitely.

Bug: 851409
Change-Id: I7efa4e616cdc1508a73c7a9f3de9d3f571569af8
Reviewed-on: https://skia-review.googlesource.com/138106
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
2 files changed