Add kAAHairline to GpuPathRenderers

With the upcoming ccpr stroking, this will no longer be the only path
renderer that can handle hairlines.

Bug: skia:
Change-Id: I45b30ccd578bee1388a3a07a234af76a19768de6
Reviewed-on: https://skia-review.googlesource.com/142272
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
6 files changed