Revert of Combined approach. (patchset #2 id:20001 of https://codereview.chromium...

Revert of Combined approach. (patchset #2 id:20001 of https://codereview.chromium.org/1356133002/ )

Reason for revert:
whee

Original issue's description:
> Combined approach.
>
> This combines some ideas from these two CLs:
>     - try stosd/w
>     - update memset16/32 inlining heuristics
>
>
> BUG=skia:4316
>
> Blinking in and out for perf.skia.org.
> TBR=reed@google.com
>
> Committed: https://skia.googlesource.com/skia/+/46243a7c02a1d5116e55a27ff59218f9c320df97

TBR=reed@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4316

Review URL: https://codereview.chromium.org/1353703006