Revert "remove third_party/etc1"

This reverts commit 9d7a73527a6df7d3523e93a6a1f964df08b94510.

Reason for revert: still used by Fiber in Google3

Original change's description:
> remove third_party/etc1
> 
> Nothing seems to reference it.
> 
> Change-Id: Ib009a7dc33d31439b11588758015a07485f56eaa
> Reviewed-on: https://skia-review.googlesource.com/99861
> Reviewed-by: Mike Klein <mtklein@chromium.org>
> Commit-Queue: Mike Klein <mtklein@chromium.org>

TBR=mtklein@chromium.org,robertphillips@google.com

Change-Id: I12b950931f0680576faefd1907a26afe22cf680f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/100460
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
6 files changed