fix path ops fuzz buster

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 597 matching lines @@
             continue;
         }
         double testDistSq = testPt.distanceSquared(i.pt(index));
         if (closestDistSq > testDistSq) {
             closestDistSq = testDistSq;
         }
     }
     return closestDistSq;
 }
 
+void SkOpSegment::findCollapsed() {
+    if (fHead.contains(&fTail)) {
+        markAllDone();
+        // move start and end to the same point
+        fHead.alignEnd(0, fHead.pt());
+        fTail.setAligned();
+    }
+}
+
 /*
  The M and S variable name parts stand for the operators.
    Mi stands for Minuend (see wiki subtraction, analogous to difference)
    Su stands for Subtrahend
  The Opp variable name part designates that the value is for the Opposite operator.
  Opposite values result from combining coincident spans.
  */
 SkOpSegment* SkOpSegment::findNextOp(SkTDArray<SkOpSpanBase*>* chase, SkOpSpanBase** nextStart,
         SkOpSpanBase** nextEnd, bool* unsortable, SkPathOp op, int xorMiMask, int xorSuMask) {
     SkOpSpanBase* start = *nextStart;
@@ skipping 1140 matching lines @@
     int absOut = abs(outerWinding);
     int absIn = abs(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();
 }