Add color correct rendering to about:flags

This feature will be enabled slowly across all platforms, and eventually
will be on by default for everyone. Leave this as a tri-state option
(default, enable, disable), although at the moment is never on by
default.

BUG=667431

Review-Url: https://codereview.chromium.org/2807423002
Cr-Commit-Position: refs/heads/master@{#464683}
4 files changed