[serializer] make snapshot reproducible.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 761ad3c1fbb7d8e8332891e562c73f626833c1ed..c5134194036b4dbbae66085b0524cec3047b4912 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -5392,6 +5392,10 @@ void Heap::SetStackLimits() {
       (isolate_->stack_guard()->real_jslimit() & ~kSmiTagMask) | kSmiTag);
 }
 
+void Heap::ClearStackLimits() {
+  roots_[kStackLimitRootIndex] = Smi::FromInt(0);
+  roots_[kRealStackLimitRootIndex] = Smi::FromInt(0);
+}
 
 void Heap::PrintAlloctionsHash() {
   uint32_t hash = StringHasher::GetHashCore(raw_allocations_hash_);