Check in codegen test expectations.

test/codegen/expect/language/map_literal1_test_none_multi.js

+dart_library.library('language/map_literal1_test_none_multi', null, /* Imports */[
+  'dart_sdk'
+], function load__map_literal1_test_none_multi(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const map_literal1_test_none_multi = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  let const$;
+  map_literal1_test_none_multi.main = function() {
+    let m = const$ || (const$ = dart.const(dart.map({a: 0})));
+  };
+  dart.fn(map_literal1_test_none_multi.main, VoidTodynamic());
+  // Exports:
+  exports.map_literal1_test_none_multi = map_literal1_test_none_multi;
+});