Revert "Remove Expect from core library."

tests/compiler/dart2js/pretty_parameter_test.dart

 // Copyright (c) 2011, 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.
 // Test that parameters keep their names in the output.
 
-import "package:expect/expect.dart";
 import 'compiler_helper.dart';
 
 const String FOO = r"""
 void foo(var a, var b) {
 }
 """;
 
 const String BAR = r"""
 void bar(var eval, var $eval) {
 }
@@ skipping 69 matching lines @@
   checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
 
   generated = compile(NO_LOCAL, entry: 'foo');
   Expect.isFalse(generated.contains('var'));
 
   generated = compile(PARAMETER_INIT, entry: 'foo');
   Expect.isTrue(generated.contains('var result = test === true ? 42 : start'));
   // Check that there is only one var declaration.
   checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
 }