Make xformer class for SkCSXCanvas, use for draw loopers

Fixes draw looper gms in gbr-8888 config.

Bug: skia:
Change-Id: I0a9306cc0523c82f2ad9516752d79c1d86b1e295
Reviewed-on: https://skia-review.googlesource.com/10644
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/gn/core.gni b/gn/core.gni
index 083b2f5..fa65f25 100644
--- a/gn/core.gni
+++ b/gn/core.gni
@@ -87,6 +87,8 @@
   "$_src/core/SkColorSpace_ICC.cpp",
   "$_src/core/SkColorSpaceXform.cpp",
   "$_src/core/SkColorSpaceXformCanvas.cpp",
+  "$_src/core/SkColorSpaceXformer.cpp",
+  "$_src/core/SkColorSpaceXformer.h",
   "$_src/core/SkColorSpaceXform_A2B.cpp",
   "$_src/core/SkColorSpaceXform_A2B.h",
   "$_src/core/SkColorTable.cpp",