Outsetting in perspective case outsets the original homogeneous quad
points rather than the homogenized 2d points in order to avoid seaming
issues along shared edges.
Currently there is no way to trigger this from the public API and it
is tested by directly accessing GrRenderTargetContext from the added gm.
Change-Id: I24e0d53cc5821c8c8be07c23aca5bfafb4935c33
Reviewed-on: https://skia-review.googlesource.com/157600
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
