Revert "Remove Expect from core library."

tests/language/if_and_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.
 
-import "package:expect/expect.dart";
-
 // The "if (negative) res2 |= 3" below can be emitted as negative && (res2 |= 3)
 // in JavaScript. Dart2js produced the wrong output.
 
 _shiftRight(x, y) => x;
 int64_bits(x) => x;
 
 class A {
   opshr(int n, a2) {
     int res2;
     bool negative = a2 == 496;
 
     res2 = _shiftRight(a2, n);
     if (negative) {
       res2 |= 3;
     }
     return int64_bits(res2);
   }
 }
 
 main() {
   var a = new A();
   var t;
   for (int i = 0; i < 3; i++) {
     t = a.opshr(99, 496);
   }
   Expect.equals(499, t);
 }