Check in codegen test expectations.

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

+dart_library.library('lib/html/exceptions_test', null, /* Imports */[
+  'dart_sdk',
+  'unittest'
+], function load__exceptions_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_config = unittest.html_config;
+  const unittest$ = unittest.unittest;
+  const src__matcher__expect = unittest.src__matcher__expect;
+  const exceptions_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  exceptions_test.main = function() {
+    html_config.useHtmlConfiguration();
+    unittest$.test('EventException', dart.fn(() => {
+      let event = html.Event.new('Event');
+      try {
+        html.document[dartx.dispatchEvent](event);
+      } catch (e) {
+        if (html.DomException.is(e)) {
+          src__matcher__expect.expect(e[dartx.name], html.DomException.INVALID_STATE);
+        } else
+          throw e;
+      }
+
+    }, VoidTodynamic()));
+  };
+  dart.fn(exceptions_test.main, VoidTodynamic());
+  // Exports:
+  exports.exceptions_test = exceptions_test;
+});