pathops coincidence and security rewrite

src/pathops/SkReduceOrder.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 "SkReduceOrder.h"
 
 int SkReduceOrder::reduce(const SkDLine& line) {
     fLine[0] = line[0];
@@ skipping 60 matching lines @@
         }
     }
     for (index = 0; index < 3; ++index) {
         if (AlmostEqualUlps(quad[index].fX, quad[minX].fX)) {
             minXSet |= 1 << index;
         }
         if (AlmostEqualUlps(quad[index].fY, quad[minY].fY)) {
             minYSet |= 1 << index;
         }
     }
+    if ((minXSet & 0x05) == 0x5 && (minYSet & 0x05) == 0x5) { // test for degenerate
+        // this quad starts and ends at the same place, so never contributes
+        // to the fill
+        return coincident_line(quad, fQuad);
+    }
     if (minXSet == 0x7) {  // test for vertical line
-        if (minYSet == 0x7) {  // return 1 if all three are coincident
-            return coincident_line(quad, fQuad);
-        }
         return vertical_line(quad, fQuad);
     }
     if (minYSet == 0x7) {  // test for horizontal line
         return horizontal_line(quad, fQuad);
     }
     int result = check_linear(quad, minX, maxX, minY, maxY, fQuad);
     if (result) {
         return result;
     }
     fQuad = quad;
@@ skipping 176 matching lines @@
     cubic.set(a);
     SkReduceOrder reducer;
     int order = reducer.reduce(cubic, kAllow_Quadratics);
     if (order == 2 || order == 3) {  // cubic became line or quad
         for (int index = 0; index < order; ++index) {
             *reducePts++ = reducer.fQuad[index].asSkPoint();
         }
     }
     return SkPathOpsPointsToVerb(order - 1);
 }