Check in codegen test expectations.

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

+dart_library.library('lib/html/audiobuffersourcenode_test', null, /* Imports */[
+  'dart_sdk',
+  'unittest'
+], function load__audiobuffersourcenode_test(exports, dart_sdk, unittest) {
+  'use strict';
+  const core = dart_sdk.core;
+  const web_audio = dart_sdk.web_audio;
+  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 audiobuffersourcenode_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  let VoidTovoid = () => (VoidTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [])))();
+  audiobuffersourcenode_test.main = function() {
+    html_individual_config.useHtmlIndividualConfiguration();
+    unittest$.group('supported', dart.fn(() => {
+      unittest$.test('supported', dart.fn(() => {
+        src__matcher__expect.expect(web_audio.AudioContext[dartx.supported], true);
+      }, VoidTodynamic()));
+    }, VoidTovoid()));
+    unittest$.group('functional', dart.fn(() => {
+      unittest$.test('createBuffer', dart.fn(() => {
+        if (dart.test(web_audio.AudioContext[dartx.supported])) {
+          let ctx = web_audio.AudioContext.new();
+          let node = ctx[dartx.createBufferSource]();
+          src__matcher__expect.expect(web_audio.AudioBufferSourceNode.is(node), src__matcher__core_matchers.isTrue);
+          node[dartx.start](ctx[dartx.currentTime], 0, 2);
+          src__matcher__expect.expect(web_audio.AudioBufferSourceNode.is(node), src__matcher__core_matchers.isTrue);
+        }
+      }, VoidTodynamic()));
+    }, VoidTovoid()));
+  };
+  dart.fn(audiobuffersourcenode_test.main, VoidTodynamic());
+  // Exports:
+  exports.audiobuffersourcenode_test = audiobuffersourcenode_test;
+});