fix path ops fuzz bug

src/pathops/SkOpSegment.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 "SkOpCoincidence.h"
 #include "SkOpContour.h"
 #include "SkOpSegment.h"
 #include "SkPathWriter.h"
@@ skipping 1279 matching lines @@
             if (swapped) {
                 SkTSwap(priorPtT, ptT);
             }
         }
     } while ((spanBase = spanBase->final() ? nullptr : spanBase->upCast()->next()));
     clear_visited(&fHead);
     return false;
 }
 
 // if a span has more than one intersection, merge the other segments' span as needed
-void SkOpSegment::moveMultiples() {
+bool SkOpSegment::moveMultiples() {
     debugValidate();
     SkOpSpanBase* test = &fHead;
     do {
         int addCount = test->spanAddsCount();
-        SkASSERT(addCount >= 1);
+        if (addCount < 1) {
+            return false;
+        }
         if (addCount == 1) {
             continue;
         }
         SkOpPtT* startPtT = test->ptT();
         SkOpPtT* testPtT = startPtT;
         do {  // iterate through all spans associated with start
             SkOpSpanBase* oppSpan = testPtT->span();
             if (oppSpan->spanAddsCount() == addCount) {
                 continue;
             }
@@ skipping 70 matching lines @@
                     goto checkNextSpan;
                 }
         tryNextSpan: 
                 ;
             } while (oppTest != oppLast && (oppTest = oppTest->upCast()->next()));
         } while ((testPtT = testPtT->next()) != startPtT);
 checkNextSpan: 
         ;
     } while ((test = test->final() ? nullptr : test->upCast()->next()));
     debugValidate();
+    return true;
 }
 
 // Move nearby t values and pts so they all hang off the same span. Alignment happens later.
 void SkOpSegment::moveNearby() {
     debugValidate();
     SkOpSpanBase* spanS = &fHead;
     do {
         SkOpSpanBase* test = spanS->upCast()->next();
         SkOpSpanBase* next;
         if (spanS->contains(test)) {
@@ skipping 369 matching lines @@
     int absOut = SkTAbs(outerWinding);
     int absIn = SkTAbs(innerWinding);
     bool result = absOut == absIn ? outerWinding < 0 : absOut < absIn;
     return result;
 }
 
 int SkOpSegment::windSum(const SkOpAngle* angle) const {
     const SkOpSpan* minSpan = angle->start()->starter(angle->end());
     return minSpan->windSum();
 }