Add gamma/sRGB tag to SkImageInfo

This reverts commit 1cbc68f9659f15206d920dacd434ddf4b658ad1f.

requires this to land in blink https://codereview.chromium.org/531883002/

R=fmalita@google.com, reed@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/527073003
4 files changed