fix asan bug triggered by pathops fuzz tests

src/pathops/SkOpSegment.h

Index: src/pathops/SkOpSegment.h
diff --git a/src/pathops/SkOpSegment.h b/src/pathops/SkOpSegment.h
index 2a51d349feb3326f5e2d0f1c95fdbf2006fbf51a..1d67b1c1318515d5e6018bd0d7ff201cd3dd26a3 100644
--- a/src/pathops/SkOpSegment.h
+++ b/src/pathops/SkOpSegment.h
@@ -337,6 +337,9 @@ public:
     void setUpWinding(SkOpSpanBase* start, SkOpSpanBase* end, int* maxWinding, int* sumWinding) {
         int deltaSum = SpanSign(start, end);
         *maxWinding = *sumWinding;
+        if (*sumWinding == SK_MinS32) {

[dogben, 2016/06/29 20:46:17]

It appears that SpanSign can return a value > 1 if windValue() is > 1. Should
this instead check sumWinding - Sk_MinS32 <= deltaSum?

+          return;
+        }
         *sumWinding -= deltaSum;
     }