Revert "Remove Expect from core library."

tests/language/implicit_scope_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 if, while etc create an implicit scope if the body
 // is not a compound statement.
 
-import "package:expect/expect.dart";
-
 class ImplicitScopeTest {
   static bool alwaysTrue() {
     return 1 + 1 == 2;
   }
   static testMain() {
     var a = "foo";
     var b;
     if (alwaysTrue()) var a = "bar"; else var b = a;
     Expect.equals("foo", a);
     Expect.equals(null, b);
 
     while (!alwaysTrue()) var a = "bar", b = "baz";
     Expect.equals("foo", a);
     Expect.equals(null, b);
 
     for (int i = 0; i < 10; i++) var a = "bar", b = "baz";
     Expect.equals("foo", a);
     Expect.equals(null, b);
 
     do var a = "bar", b = "baz"; while("black" == "white");
     Expect.equals("foo", a);
     Expect.equals(null, b);
   }
 }
 
 main() {
   ImplicitScopeTest.testMain();
 }