Revert "Remove Expect from core library."

tests/language/generic_inheritance_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 verifying that the type argument vector of subclasses are properly
 // initialized by the class finalizer.
 
-import "package:expect/expect.dart";
-
 class A<T> { A(); }
 class B extends A<Object> { B(); }
 class C extends B { C(); }
 
 main() {
   var a = new A<String>();
   var b = new B();
   var c = new C();
   Expect.isTrue(a is Object);
   Expect.isTrue(a is A<Object>);
   Expect.isTrue(a is A<String>);
   Expect.isTrue(a is !A<int>);
   Expect.isTrue(b is Object);
   Expect.isTrue(b is A<Object>);
   Expect.isTrue(b is !A<String>);
   Expect.isTrue(b is Object);
   Expect.isTrue(c is Object);
   Expect.isTrue(c is A<Object>);
   Expect.isTrue(c is !A<String>);
   Expect.isTrue(c is B);
 }