fix some 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 1244 matching lines @@
                 this->release(head, coin);
                 continue;
             }
             coin->setOppPtTEnd(kept);
         }
     } while ((coin = coin->next()));
 }
 
 // Please keep this in sync with debugMark()
 /* this sets up the coincidence links in the segments when the coincidence crosses multiple spans */
-void SkOpCoincidence::mark(DEBUG_COIN_DECLARE_ONLY_PARAMS()) {
+bool SkOpCoincidence::mark(DEBUG_COIN_DECLARE_ONLY_PARAMS()) {
     DEBUG_SET_PHASE();
     SkCoincidentSpans* coin = fHead;
     if (!coin) {
-        return;
+        return true;
     }
     do {
-        SkOpSpan* start = coin->coinPtTStartWritable()->span()->upCast();
+        SkOpSpanBase* startBase = coin->coinPtTStartWritable()->span();
+        FAIL_IF(!startBase->upCastable());
+        SkOpSpan* start = startBase->upCast();
         SkASSERT(!start->deleted());
         SkOpSpanBase* end = coin->coinPtTEndWritable()->span();
         SkOPASSERT(!end->deleted());
         SkOpSpanBase* oStart = coin->oppPtTStartWritable()->span();
         SkOPASSERT(!oStart->deleted());
         SkOpSpanBase* oEnd = coin->oppPtTEndWritable()->span();
         SkASSERT(!oEnd->deleted());
         bool flipped = coin->flipped();
         if (flipped) {
             SkTSwap(oStart, oEnd);
         }
         /* coin and opp spans may not match up. Mark the ends, and then let the interior
            get marked as many times as the spans allow */
         start->insertCoincidence(oStart->upCast());
         end->insertCoinEnd(oEnd);
         const SkOpSegment* segment = start->segment();
         const SkOpSegment* oSegment = oStart->segment();
         SkOpSpanBase* next = start;
         SkOpSpanBase* oNext = oStart;
         bool ordered = coin->ordered();
         while ((next = next->upCast()->next()) != end) {
+            FAIL_IF(!next->upCastable());
             SkAssertResult(next->upCast()->insertCoincidence(oSegment, flipped, ordered));
         }
         while ((oNext = oNext->upCast()->next()) != oEnd) {
-            SkAssertResult(oNext->upCast()->insertCoincidence(segment, flipped, ordered));
+            FAIL_IF(!oNext->upCast()->insertCoincidence(segment, flipped, ordered));
         }
     } while ((coin = coin->next()));
+    return true;
 }
 
 // Please keep in sync with debugMarkCollapsed()
 void SkOpCoincidence::markCollapsed(SkCoincidentSpans* coin, SkOpPtT* test) {
     SkCoincidentSpans* head = coin;
     while (coin) {
         if (coin->collapsed(test)) {
             if (zero_or_one(coin->coinPtTStart()->fT) && zero_or_one(coin->coinPtTEnd()->fT)) {
                 coin->coinPtTStartWritable()->segment()->markAllDone();
             }
@@ skipping 51 matching lines @@
     }
     do {
         if (coin->coinPtTStart()->segment() == deleted
                 || coin->coinPtTEnd()->segment() == deleted
                 || coin->oppPtTStart()->segment() == deleted
                 || coin->oppPtTEnd()->segment() == deleted) {
             this->release(fHead, coin);
         }
     } while ((coin = coin->next()));
 }