Revert of Gamma correction for distance field text. (https://codereview.chromium...

Revert of Gamma correction for distance field text. (https://codereview.chromium.org/258883002/)

Reason for revert:
Memory leaks. I suspect this is due to the lack of destructors in SkAutoGlyphCache

Original issue's description:
> Gamma correction for distance field text.
>
> Handles both non-LCD and LCD text. Uses a texture to look up the gamma correction values for a given text color or luminance.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/4d517fdbb145cb95e5e935470df331e1b6667cfc

NOTRY=true
NOTREECHECKS=true
R=reed@google.com, bungeman@google.com, robertphillips@google.com, bsalomon@google.com, jvanverth@google.com, mtklein@google.com

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/323513005