Revert "Remove Expect from core library."

tests/corelib/reg_exp_all_matches_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.
 
-import "package:expect/expect.dart";
-
 // Dart test program for RegExp.allMatches.
 
 class RegExpAllMatchesTest {
   static testIterator() {
     var matches = new RegExp("foo").allMatches("foo foo");
     Iterator it = matches.iterator;
     Expect.isTrue(it.moveNext());
     Expect.equals('foo', it.current.group(0));
     Expect.isTrue(it.moveNext());
     Expect.equals('foo', it.current.group(0));
@@ skipping 92 matching lines @@
     testEvery();
     testSome();
     testIsEmpty();
     testGetCount();
   }
 }
 
 main() {
   RegExpAllMatchesTest.testMain();
 }