fix path ops assert

git-svn-id: http://skia.googlecode.com/svn/trunk@8602 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/pathops/SkPathOpsCommon.cpp b/src/pathops/SkPathOpsCommon.cpp
index 1a6f0f5..93f9cd4 100644
--- a/src/pathops/SkPathOpsCommon.cpp
+++ b/src/pathops/SkPathOpsCommon.cpp
@@ -89,7 +89,7 @@
             return 0;
         }
         result = bestSeg->windingAtT(*bestHit, bestTIndex, bestOpp, bestDx);
-        SkASSERT(*bestDx);
+        SkASSERT(result == SK_MinS32 || *bestDx);
     }
     double baseT = current->t(index);
     double endT = current->t(endIndex);