Add/promote gamma helpers to SkColorSpace_Base

When decoding images with strange transfer functions, we need to
pick an "equivalent" drawable format and color space. These help
when doing that.

Our default answer is to use F16 linear, but some GPUs may not
be able to draw that, in which case we'll fall back to sRGB 8888.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4453

Change-Id: I7f7342423d2a57fb45c965e1a023d255cdafedee
Reviewed-on: https://skia-review.googlesource.com/4453
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Matt Sarett <msarett@google.com>

0 files changed, 0 insertions, 0 deletions