Revert "Remove compressed (ETC1) texture support from Ganesh"

Revert "Remove compressed (ETC1) texture support from Ganesh"

This reverts commit ee26363aaae62db2a851f2873e2405a9cf7f995a.

Reason for revert: Failing Google 3 roll.

Original change's description:
> Remove compressed (ETC1) texture support from Ganesh
>
> Change-Id: If4cf286df87ea87338aba47001d90a5fcc4f2667
> Reviewed-on: https://skia-review.googlesource.com/17456
> Commit-Queue: Robert Phillips <robertphillips@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>
>

TBR=bsalomon@google.com,robertphillips@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: Ie1a57187287e03600a69e374501478e93c41415c
Reviewed-on: https://skia-review.googlesource.com/17527
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>