fix valgrind

src/pathops/SkPathOpsOp.cpp

Index: src/pathops/SkPathOpsOp.cpp
diff --git a/src/pathops/SkPathOpsOp.cpp b/src/pathops/SkPathOpsOp.cpp
index 64a6e6ee6469527678be5cad095c59021fe8f73d..4e3ec4aad3459919ce9546b160985c4f2b6e1c8e 100644
--- a/src/pathops/SkPathOpsOp.cpp
+++ b/src/pathops/SkPathOpsOp.cpp
@@ -107,8 +107,8 @@ static bool bridgeOp(SkTDArray<SkOpContour* >& contourList, const SkPathOp op,
     SkPoint lastTopLeft;
     SkPoint topLeft = {SK_ScalarMin, SK_ScalarMin};
     do {
-        SkOpSpanBase* start;
-        SkOpSpanBase* end;
+        SkOpSpanBase* start = NULL;
+        SkOpSpanBase* end = NULL;
         bool topDone;
         bool onlyVertical = false;
         lastTopLeft = topLeft;