fix 0.499999f rounding case for triangles

Bug: skia:7994
Change-Id: I83bb309a2c8fb0bddaf78ba32c0a07537e483900
Reviewed-on: https://skia-review.googlesource.com/129648
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed