Revert of Revert of add gamma/sRGB to SkImageInfo (patchset #1 of https://codereview.chromium.org/512243002/)

Reason for revert:
this revert was premature -- the chrome canary I looked at is old, and newer ones were green. So trying again...

Original issue's description:
> 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
>
> TBR=bungeman@google.com,bsalomon@google.com
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/dc53701216c0e9f98eacf6c0cda769ebbd200b59

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/511363002
4 files changed