Revert "Remove Expect from core library."

tests/compiler/dart2js/type_inference3_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "package:expect/expect.dart";
 import 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
 sum(param0, param1) {
   var sum = 0;
   for (var i = param0; i < param1; i += 1) sum = sum + i;
   return sum;
 }
 """;
 
 main() {
   String generated = compile(TEST_ONE, entry: 'sum');
   RegExp regexp = new RegExp(getNumberTypeCheck('(param0|a)'));
   Expect.isTrue(regexp.hasMatch(generated));
   regexp = new RegExp(getNumberTypeCheck('(param1|b)'));
   Expect.isTrue(regexp.hasMatch(generated));
 }