Get rid of obsolete unchecked accessors.

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index 2ea09f89c33eba6ba8775bc0394086deeabe2f93..b1aa0edad43e894698ebfcaf2077ed905b6b9c2b 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -1297,7 +1297,7 @@ void PartialSerializer::SerializeObject(
     // The code-caches link to context-specific code objects, which
     // the startup and context serializes cannot currently handle.
     ASSERT(Map::cast(heap_object)->code_cache() ==
-           heap_object->GetHeap()->raw_unchecked_empty_fixed_array());
+           heap_object->GetHeap()->empty_fixed_array());
   }
 
   int root_index;