pathops debug globals use atomic increment

src/pathops/SkOpSegment.h

Index: src/pathops/SkOpSegment.h
diff --git a/src/pathops/SkOpSegment.h b/src/pathops/SkOpSegment.h
index b6eab86a7fbfa39cdc668c60ea1cb46eb3a68c38..1eaef69847fdde200bb176255d69c016f4e1da05 100644
--- a/src/pathops/SkOpSegment.h
+++ b/src/pathops/SkOpSegment.h
@@ -14,13 +14,17 @@
 #include "SkTArray.h"
 #include "SkTDArray.h"
 
+#if defined(SK_DEBUG) || !FORCE_RELEASE
+#include "SkThread.h"
+#endif
+
 class SkPathWriter;
 
 class SkOpSegment {
 public:
     SkOpSegment() {
 #if defined(SK_DEBUG) || !FORCE_RELEASE
-        fID = ++SkPathOpsDebug::gSegmentID;
+        fID = sk_atomic_inc(&SkPathOpsDebug::gSegmentID);
 #endif
     }