More color space improvements to DM

Added P3 configs (tagged surface and SkColorSpaceXformCanvas)

Added logic to tag the output PNGs when using a xform canvas,
so the images look correct in Chrome (and work correctly with
skdiff).

We don't use the gamma_correct tag for much in gold, but only
set it for outputs with a linear transfer function.

Change-Id: Iee713682e5010b0bd3212538a6dcb201ae4e8592
Reviewed-on: https://skia-review.googlesource.com/142170
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed