Revert "Remove Expect from core library."

tests/language/function_literals_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";
-
 /**
  * Test various forms of function literals.
  */
 typedef int IntFunc(int);
 
 class FunctionLiteralsTest {
   static void checkIntFunction(expected, int f(x), arg) {
     Expect.equals(expected, f(arg));
   }
 
@@ skipping 63 matching lines @@
     checkIntFunction(42, func2, 42);
     checkIntFunction(42, func3, 42);
     checkIntFunction(42, func4, 42);
   }
 }
 
 
 main() {
   FunctionLiteralsTest.testMain();
 }