Revert "clean up SK_SUPPORT_LEGACY_A8_MASKBLITTER"

This reverts commit ae6c5c08be769ec78a028cc69a1c59306e2a0515.

Reason for revert: Android still is.

Original change's description:
> clean up SK_SUPPORT_LEGACY_A8_MASKBLITTER
> 
> cannot find anyone defining it
> 
> Change-Id: Ia93555b4d8fa1c07dd932dc39fe8854518f1455e
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207720
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com

Change-Id: Ib9dbcb394f522fe2bd1e5be7a814952cc5d62b88
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207848
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed