Fix SDF generation for pixel-aligned paths (take two)

Cherry-pick to M56

BUG=668550

Change-Id: Ic771818bd5a4a46b83fdb82b69b98cb6b93a23a2
Reviewed-on: https://skia-review.googlesource.com/5697
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-on: https://skia-review.googlesource.com/6413
3 files changed