[compiler] Delete extra map check in StringIterator.

test/unittests/compiler/js-builtin-reducer-unittest.cc

Index: test/unittests/compiler/js-builtin-reducer-unittest.cc
diff --git a/test/unittests/compiler/js-builtin-reducer-unittest.cc b/test/unittests/compiler/js-builtin-reducer-unittest.cc
index 419cc7224e95fe1b0a3f9bfaae0fe42232e06f6b..e3857ef526cc249208b58fe503f2ee258f92138b 100644
--- a/test/unittests/compiler/js-builtin-reducer-unittest.cc
+++ b/test/unittests/compiler/js-builtin-reducer-unittest.cc
@@ -33,8 +33,10 @@ class JSBuiltinReducerTest : public TypedGraphTest {
                     &machine);
     // TODO(titzer): mock the GraphReducer here for better unit testing.
     GraphReducer graph_reducer(zone(), graph());
+
     JSBuiltinReducer reducer(&graph_reducer, &jsgraph,
-                             JSBuiltinReducer::kNoFlags, nullptr);
+                             JSBuiltinReducer::kNoFlags, nullptr,
+                             native_context());
     return reducer.Reduce(node);
   }