add conics to path ops

src/pathops/SkOpCubicHull.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkPathOpsCubic.h"
 
 static bool rotate(const SkDCubic& cubic, int zero, int index, SkDCubic& rotPath) {
     double dy = cubic[index].fY - cubic[zero].fY;
     double dx = cubic[index].fX - cubic[zero].fX;
     if (approximately_zero(dy)) {
         if (approximately_zero(dx)) {
             return false;
         }
         rotPath = cubic;
+        if (dy) {
+            rotPath[index].fY = cubic[zero].fY;
+            int mask = other_two(index, zero);
+            int side1 = index ^ mask;
+            int side2 = zero ^ mask;
+            if (approximately_equal(cubic[side1].fY, cubic[zero].fY)) {
+                rotPath[side1].fY = cubic[zero].fY;
+            }
+            if (approximately_equal(cubic[side2].fY, cubic[zero].fY)) {
+                rotPath[side2].fY = cubic[zero].fY;
+            }
+        }
         return true;
     }
     for (int index = 0; index < 4; ++index) {
         rotPath[index].fX = cubic[index].fX * dx + cubic[index].fY * dy;
         rotPath[index].fY = cubic[index].fY * dx - cubic[index].fX * dy;
     }
     return true;
 }
 
 
@@ skipping 90 matching lines @@
     int midSides = side(midPath[yMin].fY - midPath[least].fY);
     midSides ^= side(midPath[midX].fY - midPath[least].fY);
     if (midSides != 2) {  // if mid point is not between
         order[2] = most;
         return 3; // result is a triangle
     }
     order[2] = midX;
     order[3] = most;
     return 4; // result is a quadralateral
 }