Add base effect for gpu 2pt conical gradients

src/effects/gradients/SkTwoPointConicalGradient.h

Index: src/effects/gradients/SkTwoPointConicalGradient.h
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.h b/src/effects/gradients/SkTwoPointConicalGradient.h
index 71ba57f6d14b7667a6936434b1598f5b1dc9e792..041f8b8be44cd74e9c75c3da046e44a419689e7a 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.h
+++ b/src/effects/gradients/SkTwoPointConicalGradient.h
@@ -65,6 +65,9 @@ public:
     SkScalar getCenterX1() const { return SkPoint::Distance(fCenter1, fCenter2); }
     SkScalar getStartRadius() const { return fRadius1; }
     SkScalar getDiffRadius() const { return fRadius2 - fRadius1; }
+    const SkPoint& getStartCenter() const { return fCenter1; }
+    const SkPoint& getEndCenter() const { return fCenter2; }
+    SkScalar getEndRadius() const { return fRadius2; }
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTwoPointConicalGradient)