Add quad to cubic bezier conversion utility to SkPath.

include/core/SkPath.h

Index: include/core/SkPath.h
diff --git a/include/core/SkPath.h b/include/core/SkPath.h
index 4ce816f92f12d04020b63e98801274ee5a9cd4a1..9d8421fd6f1a0e8892c8bfa459af0565e6d9e0d2 100644
--- a/include/core/SkPath.h
+++ b/include/core/SkPath.h
@@ -547,6 +547,13 @@ public:
                                    SkScalar w, SkPoint pts[], int pow2);
 
     /**
+     *  Given 3 points on a quadratic bezier, use degree elevation to
+     *  convert it into the cubic fitting the same curve. The new cubic
+     *  curve is returned in dst[0..3].
+     */
+    static void ConvertQuadToCubic(const SkPoint src[3], SkPoint dst[4]);
+
+    /**
      *  Returns true if the path specifies a rectangle.
      *
      *  If this returns false, then all output parameters are ignored, and left