Add SkDefaultXform as a catch-all to handle color conversions

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 b2d5818e84e31b5e4e58ffcfa8e170be23d07b4b..247ae120d275eb09d6efcc80193d5b69e5f3f001 100644
--- a/src/core/SkColorSpace_Base.h
+++ b/src/core/SkColorSpace_Base.h
@@ -78,6 +78,11 @@ public:
         return fRed.isValue() && fGreen.isValue() && fBlue.isValue();
     }
 
+    const SkGammaCurve& operator[](int i) {
+        SkASSERT(0 <= i && i < 3);
+        return (&fRed)[i];
+    }
+
     const SkGammaCurve fRed;
     const SkGammaCurve fGreen;
     const SkGammaCurve fBlue;
@@ -117,6 +122,8 @@ public:
 
     const sk_sp<SkGammas>& gammas() const { return fGammas; }
 
+    SkColorLookUpTable* colorLUT() const { return fColorLUT.get(); }
+
     /**
      *  Writes this object as an ICC profile.
      */