use pathops utils to improve precision of cubic chopping in scan converter

src/pathops/SkDCubicLineIntersection.cpp

Index: src/pathops/SkDCubicLineIntersection.cpp
diff --git a/src/pathops/SkDCubicLineIntersection.cpp b/src/pathops/SkDCubicLineIntersection.cpp
index f658b09f0bb0931ab62fe08a7617cea1c75b94aa..ee1e3d3a341c19ad48bbcaf3c9e41063b238456c 100644
--- a/src/pathops/SkDCubicLineIntersection.cpp
+++ b/src/pathops/SkDCubicLineIntersection.cpp
@@ -425,3 +425,13 @@ int SkIntersections::intersectRay(const SkDCubic& cubic, const SkDLine& line) {
     }
     return fUsed;
 }
+
+// SkDCubic accessors to Intersection utilities
+
+int SkDCubic::horizontalIntersect(double yIntercept, double roots[3]) const {
+    return LineCubicIntersections::HorizontalIntersect(*this, yIntercept, roots);
+}
+
+int SkDCubic::verticalIntersect(double xIntercept, double roots[3]) const {
+    return LineCubicIntersections::VerticalIntersect(*this, xIntercept, roots);
+}