Revert of add gamma/sRGB to SkImageInfo (patchset #4 of https://codereview.chromium.org/514753002/)

Reason for revert:
breaks linker on chrome -- may need SK_API, but not sure.

Original issue's description:
> add gamma/sRGB to SkImageInfo
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/615c369777258231054840a88cdb74c68c382485

R=bungeman@google.com, bsalomon@google.com
TBR=bsalomon@google.com, bungeman@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: reed@google.com

Review URL: https://codereview.chromium.org/512243002
4 files changed