fix path ops fuzz buster

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 550 matching lines @@
         if (coin->fCoinPtTEnd->deleted()) {
             coin->fCoinPtTEnd = coin->fCoinPtTEnd->doppelganger();
         }
         if (coin->fOppPtTStart->deleted()) {
             coin->fOppPtTStart = coin->fOppPtTStart->doppelganger();
         }
         if (coin->fOppPtTEnd->deleted()) {
             coin->fOppPtTEnd = coin->fOppPtTEnd->doppelganger();
         }
     } while ((coin = coin->fNext));
+    coin = fHead;
+    SkCoincidentSpans** priorPtr = &fHead;
+    do {
+        if (coin->fCoinPtTStart->collapsed(coin->fCoinPtTEnd)
+                || coin->fOppPtTStart->collapsed(coin->fOppPtTEnd)) {
+            *priorPtr = coin->fNext;
+            continue;
+        }
+        priorPtr = &coin->fNext;
+    } while ((coin = coin->fNext));
 }
 
 void SkOpCoincidence::fixUp(SkOpPtT* deleted, SkOpPtT* kept) {
     SkCoincidentSpans* coin = fHead;
     if (!coin) {
         return;
     }
     do {
         if (coin->fCoinPtTStart == deleted) {
             if (coin->fCoinPtTEnd->span() == kept->span()) {
@@ skipping 69 matching lines @@
     *overS = SkTMax(SkTMin(coin1s->fT, coin1e->fT), SkTMin(coin2s->fT, coin2e->fT));
     *overE = SkTMin(SkTMax(coin1s->fT, coin1e->fT), SkTMax(coin2s->fT, coin2e->fT));
     return *overS < *overE;
 }
 
 bool SkOpCoincidence::testForCoincidence(const SkCoincidentSpans* outer, SkOpPtT* testS,
         SkOpPtT* testE) const {
     return testS->segment()->testForCoincidence(testS, testE, testS->span(),
             testE->span(), outer->fCoinPtTStart->segment(), 120000);  // FIXME: replace with tuned
 }