Revert "Remove Expect from core library."

tests/compiler/dart2js/minify_many_locals_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';
 
 main() {
   var buffer = new StringBuffer();
   buffer.write("var foo(");
   for (int i = 0; i < 2000; i++) {
     buffer.write("x$i, ");
   }
   buffer.write("x) { int i = ");
   for (int i = 0; i < 2000; i++) {
@@ skipping 15 matching lines @@
 
   re = new RegExp(r"Z8,Z9,aa0,aa1,aa2");
   Expect.isTrue(re.hasMatch(generated));
 
   re = new RegExp(r"aa9,ab0,ab1");
   Expect.isTrue(re.hasMatch(generated));
 
   re = new RegExp(r"aZ9,ba0,ba1");
   Expect.isTrue(re.hasMatch(generated));
 }