Revert "Remove Expect from core library."

tests/language/new_statement_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 a new statement by itself.
 
-import "package:expect/expect.dart";
-
 class A {
   int a;
   int b;
   static int c;
   static int d;
 
   A(int x, int y) : a = x, b = y {
     A.c = x;
     A.d = y;
   }
 }
 
 class NewStatementTest {
   static testMain() {
     new A(10, 20);
     Expect.equals(10, A.c);
     Expect.equals(20, A.d);
   }
 }
 
 
 main() {
   NewStatementTest.testMain();
 }