Remove Expect from core library.

tests/language/inline_argument_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.
 // Test that when inlining A.foo, we're not evaluating the argument
 // twice.
 
+import "package:expect/expect.dart";
+
 class A {
   var field = 0;
 
   foo(b) {
     Expect.equals(0, b);
     Expect.equals(0, b);
   }
 
   bar() {
     foo(field++);
   }
 }
 
 main() {
   var a = new A();
   a.bar();
   Expect.equals(1, a.field);
 }