Add effect-based clip for nine-patch SkRRects.

include/core/SkRRect.h

Index: include/core/SkRRect.h
diff --git a/include/core/SkRRect.h b/include/core/SkRRect.h
index 9878b54fdc0019be255f3c18551b748cd9dce8aa..c09d2d46fe85aed3ca925d2419fcb98838138225 100644
--- a/include/core/SkRRect.h
+++ b/include/core/SkRRect.h
@@ -103,6 +103,17 @@ public:
 
     bool allCornersCircular() const;
 
+    /**
+     * Are both x-radii the same on the two left corners, and similar for the top, right, and
+     * bottom. When this is the case the four ellipse centers form a rectangle.
+     */
+    bool isNinePatch() const {
+        return fRadii[kUpperLeft_Corner].fX == fRadii[kLowerLeft_Corner].fX &&
+               fRadii[kUpperRight_Corner].fX == fRadii[kLowerRight_Corner].fX &&
+               fRadii[kUpperLeft_Corner].fY == fRadii[kUpperRight_Corner].fY &&
+               fRadii[kLowerLeft_Corner].fY == fRadii[kLowerRight_Corner].fY;
+    }
+
     SkScalar width() const { return fRect.width(); }
     SkScalar height() const { return fRect.height(); }