Revert of Add gamma/sRGB tag to SkImageInfo (patchset #1 id:1 of https://codereview.chromium.org/522813002/)

Reason for revert:
seems to be breaking layout tests in roll

Original issue's description:
> Add gamma/sRGB tag to SkImageInfo
>
> This reverts commit 64ba5fa1ff428858f803523257cd862f8b33423b.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/c89aa509d6a094bc1b18d73135343819903a9cfb

R=reed@google.com
TBR=reed@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/525113005
4 files changed