Remove Expect from core library.

tests/language/invocation_mirror_invoke_on_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";
+
 // Testing InvocationMirror.invokeOn method; test of issue 7227.
 
 var reachedSetX = 0;
 var reachedGetX = 0;
 var reachedM = 0;
 
 class A {
 
   set x(val) {
     reachedSetX = val;
@@ skipping 13 matching lines @@
 
 main () {
   var b = new B();
   b.x = 10;
   Expect.equals(10, reachedSetX);
   b.x;
   Expect.equals(1, reachedGetX);
   b.m();
   Expect.equals(1, reachedM);
 }