Revert "Make DashOp a non-legacy GrMeshDrawOp."

This reverts commit ebb38256c65f2d799dd64f0274256a0c1deffed1.

Reason for revert: Assertions on ANGLE bots

Original change's description:
> Make DashOp a non-legacy GrMeshDrawOp.
> 
> Change-Id: I84ee3c64a5af8889e9a122cbc08d70ed6b25fbab
> Reviewed-on: https://skia-review.googlesource.com/22210
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>

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

Change-Id: I886a0bd75221f05d737d8b27c6b3d8d6cce5573c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/22680
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
5 files changed