use SkColorSpaceXformer in SkShader appendStages() fallback

We've been transforming the gamut after running the legacy shader,
but now that we have SkColorSpaceXformer, we can transform the
legacy shader into the dst color space instead.

This should be both more correct and faster.

Change-Id: If017048874e6cce46837d3ecbd88dfde503fd03a
Reviewed-on: https://skia-review.googlesource.com/16373
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed