fix next kevin fuzz

src/pathops/SkOpCoincidence.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkOpCoincidence.h"
 #include "SkOpSegment.h"
 #include "SkPathOpsTSect.h"
 
@@ skipping 443 matching lines @@
         double oPriorT = oStartPtT->fT;
         FAIL_IF(!startPtT->contains(oStartPtT));
         SkOPASSERT(coin->coinPtTEnd()->contains(coin->oppPtTEnd()));
         const SkOpSpanBase* start = startPtT->span();
         const SkOpSpanBase* oStart = oStartPtT->span();
         const SkOpSpanBase* end = coin->coinPtTEnd()->span();
         const SkOpSpanBase* oEnd = coin->oppPtTEnd()->span();
         FAIL_IF(oEnd->deleted());
         FAIL_IF(!start->upCastable());
         const SkOpSpanBase* test = start->upCast()->next();
+        FAIL_IF(!coin->flipped() && !oStart->upCastable());
         const SkOpSpanBase* oTest = coin->flipped() ? oStart->prev() : oStart->upCast()->next();
         FAIL_IF(!oTest);
         SkOpSegment* seg = start->segment();
         SkOpSegment* oSeg = oStart->segment();
         while (test != end || oTest != oEnd) {
             const SkOpPtT* containedOpp = test->ptT()->contains(oSeg);
             const SkOpPtT* containedThis = oTest->ptT()->contains(seg);
             if (!containedOpp || !containedThis) {
                 // choose the ends, or the first common pt-t list shared by both
                 double nextT, oNextT;
@@ skipping 1129 matching lines @@
             this->release(fHead, coin);
         }
     } while ((coin = coin->next()));
 }
 
 bool SkOpCoincidence::testForCoincidence(const SkCoincidentSpans* outer, const SkOpPtT* testS,
         const SkOpPtT* testE) const {
     return testS->segment()->testForCoincidence(testS, testE, testS->span(),
             testE->span(), outer->coinPtTStart()->segment());
 }