Revert of Add ETC1 format to SkTextureCompressor (https://codereview.chromium.org/432143002/)

Reason for revert:
Breaking Chrome.

Original issue's description:
> Add ETC1 format to SkTextureCompressor
>
> Committed: https://skia.googlesource.com/skia/+/5d8b1b44ea7636fc8e98247cb311568f277ce3a5

R=robertphillips@google.com
TBR=robertphillips@google.com
NOTREECHECKS=true
NOTRY=true

Author: krajcevski@google.com

Review URL: https://codereview.chromium.org/438443004
6 files changed