Revert "Remove Expect from core library."

tests/language/function_literals2_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.
 //
 // Dart test for new function type alias.
 
-import "package:expect/expect.dart";
-
 class FunctionLiteralsTest {
 
   static void testMain() {
     f(x) { return x * 2;}
     f(42);  // make sure it is parsed as a function call
     Expect.equals(20, f(10));
 
     int g(x) { return x * 2;}
     g(42);  // make sure it is parsed as a function call
     Expect.equals(20, g(10));
@@ skipping 50 matching lines @@
 class B {
   var f;
   int n;
   B(z) : f = ((x) => x * x) { n = z; }
   B.withZ(z) : f = ((x) { return x * x + 1; }) { n = z; }
 }
 
 main() {
   FunctionLiteralsTest.testMain();
 }