Check in codegen test expectations.

test/codegen/expect/corelib/null_test.js

Index: test/codegen/expect/corelib/null_test.js
diff --git a/test/codegen/expect/corelib/null_test.js b/test/codegen/expect/corelib/null_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..1582efe982c4f57c4ba72aaf15888e3c75afe4cb
--- /dev/null
+++ b/test/codegen/expect/corelib/null_test.js
@@ -0,0 +1,29 @@
+dart_library.library('corelib/null_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__null_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 null_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  null_test.main = function() {
+    let x = null;
+    expect$.Expect.isTrue(core.Object.is(x));
+    expect$.Expect.isTrue(dart.dynamic.is(x));
+    expect$.Expect.isTrue(!(typeof x == 'string'));
+    expect$.Expect.isTrue(!(typeof x == 'number'));
+    dart.runtimeType(x);
+    dart.toString(x);
+    dart.hashCode(x);
+    expect$.Expect.isTrue(core.identical(x, null));
+    expect$.Expect.isTrue(x == null);
+    let ts = dart.toString(x);
+    expect$.Expect.equals(dart.toString(null), dart.dcall(ts));
+  };
+  dart.fn(null_test.main, VoidTodynamic());
+  // Exports:
+  exports.null_test = null_test;
+});