Revert "Remove Expect from core library."

tests/language/method_name_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.
 
-import "package:expect/expect.dart";
-
 // Tests that methods with names "get", "set" and "operator" don't
 // cause fatal problems.
 
 // With return type.
 class A {
   int get() {return 1;}
   int set() {return 2;}
   int operator() {return 3;}
 }
 
@@ skipping 11 matching lines @@
     Expect.equals(2, a.set());
     Expect.equals(3, a.operator());
   }
   {
     B b = new B();
     Expect.equals(1, b.get());
     Expect.equals(2, b.set());
     Expect.equals(3, b.operator());
   }
 }