Revert of Stub out Skia AVX and HSW opts. (patchset #1 id:1 of https://codereview.chromium.org/2512093003/ )

Reason for revert:
Now that we're guarding against ucrt\math.h in Skia and that's rolled into Chromium, it's as good a time as ever to try turning back on Skia's AVX+ code at head.  (I intend to just leave it stubbed out like this in M56.)

Original issue's description:
> Stub out Skia AVX and HSW opts.
>
> This is hopefully temporary while we mull better options.
>
> BUG=666707
>
> Committed: https://crrev.com/2ea76e2274404af7e53cc4bb5d212b22856ee455
> Cr-Commit-Position: refs/heads/master@{#433407}

TBR=brucedawson@chromium.org,thakis@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=666707

Review-Url: https://codereview.chromium.org/2539453003
Cr-Commit-Position: refs/heads/master@{#434983}
3 files changed