Revert "converted OverdrawColorFilter to SkSL"

This reverts commit 8aa4dc9052a64d84cfd0a4330910057bd37b6bf7.

Reason for revert: strncmp getting mad

Original change's description:
> converted OverdrawColorFilter to SkSL
> 
> Bug: skia:
> Change-Id: Idcc0502758df1e60ed131a168b5c9a65a4d834a1
> Reviewed-on: https://skia-review.googlesource.com/63840
> Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

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

Change-Id: Ib78d7c878c4597918d059bddb4d61f6a7f59a511
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/63561
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
21 files changed