Extract most of the mutable state of SkShader into a separate Context object.

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 20a3da8b2e82a5c6fae7ba3ff958d196a58d6060..b1561e808e4a80a2e21f841bf3c2dcb0c8faffda 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.h
+++ b/src/effects/gradients/SkTwoPointConicalGradient.h
@@ -49,11 +49,13 @@ public:
                               const SkPoint& end, SkScalar endRadius,
                               const Descriptor&);
 
+#if 0
     virtual void shadeSpan(int x, int y, SkPMColor* dstCParam,
                            int count) SK_OVERRIDE;
     virtual bool setContext(const SkBitmap& device,
                             const SkPaint& paint,
                             const SkMatrix& matrix) SK_OVERRIDE;
+#endif
 
     virtual BitmapType asABitmap(SkBitmap* bitmap,
                                  SkMatrix* matrix,