Make snapshots reproducible.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index e8c985048455e406c77c6b4c6814261f2cb7ab41..2977787468f65623c49185a291954e6129ff1ed9 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5196,6 +5196,15 @@ class Code: public HeapObject {
 
   void ReplaceNthCell(int n, Cell* replace_with);
 
+  // The entire code object including its header is copied verbatim to the
+  // snapshot so that it can be written in one, fast, memcpy during
+  // deserialization. The deserializer will overwrite some pointers, rather
+  // like a runtime linker, but the random allocation addresses used in the
+  // mksnapshot process would still be present in the unlinked snapshot data,
+  // which would make snapshot production non-reproducible. This method wipes
+  // out the to-be-overwritten header data for reproducible snapshots.
+  inline void WipeOutHeader();
+
   class ExtraICStateStrictMode: public BitField<StrictModeFlag, 0, 1> {};
   class ExtraICStateKeyedAccessStoreMode:
       public BitField<KeyedAccessStoreMode, 1, 4> {};  // NOLINT