Cache dst LUTs in SkColorSpaceXform

This is only useful in the rare case that the dst does not
fall into one of our main paths.

But it's a good optimization, since this does happen,
and typically, the dst won't change.

ColorCodecBench z620 --nonstd --xform_only
Without Patch 511us
With Patch    348us

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3400

Change-Id: Ibf68d9ce7072680465662922f4aa15630545e3d6
Reviewed-on: https://skia-review.googlesource.com/3400
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>

0 files changed, 0 insertions, 0 deletions