Revert "Remove Expect from core library."

tests/language/switch_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.
 // Test switch statement.
 
-import "package:expect/expect.dart";
-
 class Switcher {
 
   Switcher() { }
 
   test1 (val) {
     var x = 0;
     switch (val) {
       case 1:
         x = 100; break;
       case 2:
@@ skipping 100 matching lines @@
   testSwitchIntExpression(2, 11);
   testSwitchIntExpression(3, 11);
   testSwitchIntExpression(4, 21);
   testSwitchIntExpression(5, 21);
   testSwitchIntExpression(6, 31);
   testSwitchIntExpression(7, null);
 
   testSwitchBool(true, 12);
   testSwitchBool(false, 22);
 }