a more involved path is rect bug

This is bug number ten in the series, and is the
most interesting. It exploits that the code tracks
corners 0, 2, and 3 but not corner 1.

Changing the code to track all corners is the biggest
so far, and while it (hopefully) simplifies things,
the presence of new code may signify more bugs to come.

R=robertphillips@google.com

Bug: 824145,skia::7792
Change-Id: Ia18e4d80fbed06ae6d9c89dcb4c462c5610213cc
Reviewed-on: https://skia-review.googlesource.com/121487
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>
3 files changed