fix another pathmeasure fuzz

Delete the cache of measurements if the total
length is not computable (NaN), since the individual
measurements may cause other failures later, like
finding the initial segment position.

R=kjlubick@google.com

Bug: skia:8373
Change-Id: Ibf58c261c46a5535a0a1f12cbeb94da29e33f471
Reviewed-on: https://skia-review.googlesource.com/153601
Commit-Queue: Cary Clark <caryclark@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Cary Clark <caryclark@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
1 file changed