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

This reverts commit 255bcf57ffd9db368cd66ca9697549efd799153e.

Reason for revert: layout and scuba image diffs

Original change's description:
> Add arcs as a specialized geometry to GrShape.
> 
> BUG: skia:7794
> 
> Change-Id: I484693711f48e55631732a0f4ee97e2848dec89d
> Reviewed-on: https://skia-review.googlesource.com/122900
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

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

Change-Id: I9293b8fbb535d940bca5fc30a95908416b9eb7a7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/123362
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
7 files changed