Check in codegen test expectations.

test/codegen/expect/language/hash_map_null_key_foreach_test.js

+dart_library.library('language/hash_map_null_key_foreach_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__hash_map_null_key_foreach_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const hash_map_null_key_foreach_test = Object.create(null);
+  let MapOfint$int = () => (MapOfint$int = dart.constFn(core.Map$(core.int, core.int)))();
+  let intAndintTovoid = () => (intAndintTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [core.int, core.int])))();
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  hash_map_null_key_foreach_test.main = function() {
+    let x = MapOfint$int().new();
+    x[dartx.set](1, 2);
+    x[dartx.set](null, 1);
+    let c = 0;
+    x[dartx.forEach](dart.fn((i, j) => {
+      c++;
+      expect$.Expect.isTrue(i == null || typeof i == 'number', 'int or null expected');
+    }, intAndintTovoid()));
+    expect$.Expect.equals(2, c);
+  };
+  dart.fn(hash_map_null_key_foreach_test.main, VoidTodynamic());
+  // Exports:
+  exports.hash_map_null_key_foreach_test = hash_map_null_key_foreach_test;
+});