harden pathops for pathological test

src/pathops/SkOpContour.cpp

 /*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 #include "SkIntersections.h"
 #include "SkOpContour.h"
 #include "SkPathWriter.h"
 #include "SkTSort.h"
 
 bool SkOpContour::addCoincident(int index, SkOpContour* other, int otherIndex,
         const SkIntersections& ts, bool swap) {
     SkPoint pt0 = ts.pt(0).asSkPoint();
     SkPoint pt1 = ts.pt(1).asSkPoint();
-    if (pt0 == pt1) {
+    if (pt0 == pt1 || ts[0][0] == ts[0][1] || ts[1][0] == ts[1][1]) {
         // FIXME: one could imagine a case where it would be incorrect to ignore this
         // suppose two self-intersecting cubics overlap to be coincident --
         // this needs to check that by some measure the t values are far enough apart
         // or needs to check to see if the self-intersection bit was set on the cubic segment
         return false;
     }
     SkCoincidence& coincidence = fCoincidences.push_back();
     coincidence.fOther = other;
     coincidence.fSegments[0] = index;
     coincidence.fSegments[1] = otherIndex;
@@ skipping 726 matching lines @@
         SkDebugf("%s empty contour\n", __FUNCTION__);
         SkASSERT(0);
         // FIXME: delete empty contour?
         return;
     }
     fBounds = fSegments.front().bounds();
     for (int index = 1; index < count; ++index) {
         fBounds.add(fSegments[index].bounds());
     }
 }