Add SkColorSpaceXform to the public API

gm/colorspacexform.cpp

Index: gm/colorspacexform.cpp
diff --git a/gm/colorspacexform.cpp b/gm/colorspacexform.cpp
index 34abdc4b79e7f828cbec7bde81892d6fdb322891..33320ba5a865c834e9cce31a86ba1dfe225604ef 100644
--- a/gm/colorspacexform.cpp
+++ b/gm/colorspacexform.cpp
@@ -41,9 +41,9 @@ protected:
         std::unique_ptr<SkColorSpaceXform> xform = SkColorSpaceXform::New(srcSpace.get(),
                                                                           dstSpace.get());
 
-        xform->apply(fWideGamutColors, colors, kNumColors,
-                     SkColorSpaceXform::kRGBA_F32_ColorFormat,
-                     SkColorSpaceXform::kBGRA_8888_ColorFormat, kOpaque_SkAlphaType);
+        xform->apply(SkColorSpaceXform::kRGBA_F32_ColorFormat, fWideGamutColors,
+                     SkColorSpaceXform::kBGRA_8888_ColorFormat, colors, kNumColors,
+                     kOpaque_SkAlphaType);
     }
 
     SkString onShortName() override {