Preseve tangents when converting cubics->quads in GrAAHairlinePathRenderer

Bug: chromium:847759
Change-Id: I35a6d069f732d906714a640fca59a71fd35b74ec
Reviewed-on: https://skia-review.googlesource.com/152664
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
4 files changed