[serializer] do not cache resource data pointer for native source.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index cbc6d72ad839a31822e64cbd93df6503ccca5133..8bb39abb83854fef006bea3e78421afd859f2034 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2306,8 +2306,9 @@ bool Heap::CreateInitialMaps() {
     }
 
     {  // Create a separate external one byte string map for native sources.
-      AllocationResult allocation = AllocateMap(EXTERNAL_ONE_BYTE_STRING_TYPE,
-                                                ExternalOneByteString::kSize);
+      AllocationResult allocation =
+          AllocateMap(SHORT_EXTERNAL_ONE_BYTE_STRING_TYPE,
+                      ExternalOneByteString::kShortSize);
       if (!allocation.To(&obj)) return false;
       Map* map = Map::cast(obj);
       map->SetConstructorFunctionIndex(Context::STRING_FUNCTION_INDEX);