Check in codegen test expectations.

test/codegen/expect/lib/html/performance_api_test.js

+dart_library.library('lib/html/performance_api_test', null, /* Imports */[
+  'dart_sdk',
+  'unittest'
+], function load__performance_api_test(exports, dart_sdk, unittest) {
+  'use strict';
+  const core = dart_sdk.core;
+  const html = dart_sdk.html;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const html_individual_config = unittest.html_individual_config;
+  const unittest$ = unittest.unittest;
+  const src__matcher__expect = unittest.src__matcher__expect;
+  const src__matcher__core_matchers = unittest.src__matcher__core_matchers;
+  const src__matcher__throws_matcher = unittest.src__matcher__throws_matcher;
+  const performance_api_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  let VoidTovoid = () => (VoidTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [])))();
+  performance_api_test.main = function() {
+    html_individual_config.useHtmlIndividualConfiguration();
+    unittest$.group('supported', dart.fn(() => {
+      unittest$.test('supported', dart.fn(() => {
+        src__matcher__expect.expect(html.Performance[dartx.supported], true);
+      }, VoidTodynamic()));
+    }, VoidTovoid()));
+    unittest$.group('performance', dart.fn(() => {
+      unittest$.test('PerformanceApi', dart.fn(() => {
+        let expectation = dart.test(html.Performance[dartx.supported]) ? src__matcher__core_matchers.returnsNormally : src__matcher__throws_matcher.throws;
+        src__matcher__expect.expect(dart.fn(() => {
+          let requestStart = html.window[dartx.performance][dartx.timing][dartx.requestStart];
+          let responseStart = html.window[dartx.performance][dartx.timing][dartx.responseStart];
+          let responseEnd = html.window[dartx.performance][dartx.timing][dartx.responseEnd];
+          let loading = html.window[dartx.performance][dartx.timing][dartx.domLoading];
+          let loadedStart = html.window[dartx.performance][dartx.timing][dartx.domContentLoadedEventStart];
+          let loadedEnd = html.window[dartx.performance][dartx.timing][dartx.domContentLoadedEventEnd];
+          let complete = html.window[dartx.performance][dartx.timing][dartx.domComplete];
+          let loadEventStart = html.window[dartx.performance][dartx.timing][dartx.loadEventStart];
+        }, VoidTodynamic()), expectation);
+      }, VoidTodynamic()));
+    }, VoidTovoid()));
+  };
+  dart.fn(performance_api_test.main, VoidTodynamic());
+  // Exports:
+  exports.performance_api_test = performance_api_test;
+});