[serializer] make snapshot reproducible.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 74b9d85a15aed7ce8ec43fd23986cfa8cd01b7c8..c51b282cc97f0b6bbb6378228e40f6a4707ecf8a 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1004,6 +1004,10 @@ class Heap {
   // jslimit_/real_jslimit_ variable in the StackGuard.
   void SetStackLimits();
 
+  // The stack limit is thread-dependent. To be able to reproduce the same
+  // snapshot blob, we need to reset it before serializing.
+  void ClearStackLimits();
+
   // Generated code can treat direct references to this root as constant.
   bool RootCanBeTreatedAsConstant(RootListIndex root_index);