fix path is rect flaw exposed by gold

One of the path is rect bug fixes changed
the behavior of zero-length strokes which
showed up as a change in Gold.

The bug is if a rect is defined by a
series of colinear movetos, the bounds
did not work out if the rect started
and stopped in the middle of a side.

R=robertphillips@google.com
Bug: 824145,skia:7792
Change-Id: I226545efeda03dedd928eebc120d2508b428fef0
Reviewed-on: https://skia-review.googlesource.com/122002
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>
3 files changed