Add SkColorSpacePrimaries to help with making D50 matrices

src/core/SkColorSpace_Base.h

Index: src/core/SkColorSpace_Base.h
diff --git a/src/core/SkColorSpace_Base.h b/src/core/SkColorSpace_Base.h
index 31f96dd7f9dde6552acd430b04071c9ad7cd4eaa..c8a9c751e3f91978888d69602af763f8996c0e71 100644
--- a/src/core/SkColorSpace_Base.h
+++ b/src/core/SkColorSpace_Base.h
@@ -41,7 +41,7 @@ struct SkGammas : SkRefCnt {
         }
     };
 
-    // Contains the parameters for a parametric curve.
+    // TODO: Delete this and make a bunch of name changes so the world still compiles.
     struct Params {
         //     Y = (aX + b)^g + c  for X >= d
         //     Y = eX + f          otherwise