Make TessellationHelper resettable

Change-Id: I94d22edf13b8392e1d7b84367fd65701f99a0e54
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255137
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed