Correctly clean up natives sources on tear down.

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index 1423b2349d326d2f356f69649ea38944e72c91b5..673c01f56799d997aa9e67d48afd3a318fb7b5a7 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -1295,11 +1295,11 @@ void Deserializer::ReadData(Object** current, Object** limit, int source_space,
       }
 
       case kNativesStringResource: {
+        DCHECK(!isolate_->heap()->deserialization_complete());
         int index = source_.Get();
         Vector<const char> source_vector = Natives::GetScriptSource(index);
         NativesExternalStringResource* resource =
-            new NativesExternalStringResource(isolate->bootstrapper(),
-                                              source_vector.start(),
+            new NativesExternalStringResource(source_vector.start(),
                                               source_vector.length());
         Object* resource_obj = reinterpret_cast<Object*>(resource);
         UnalignedCopy(current++, &resource_obj);