Reland "Revert "Add arcs as a specialized geometry to GrShape.""

This reverts commit 8a98bc96748d1bdaf9c2d8cfa0b672e3a035973d.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Revert "Revert "Add arcs as a specialized geometry to GrShape.""
> 
> This reverts commit af88ec37124846a0168a4ab061bf10cc6030c2d6.
> 
> Bug: skia:7794
> Change-Id: I2d0e1d7b4e025481241d823b09f5de5d0f1a13eb
> Reviewed-on: https://skia-review.googlesource.com/123627
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,robertphillips@google.com

Change-Id: Ib09a533600028b76a69b455c952f3dd12b39bdba
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:7794
Reviewed-on: https://skia-review.googlesource.com/123780
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
7 files changed