Remove Expect from core library.

tests/corelib/range_error_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";
+
 // Dart test for testing out of range exceptions on arrays.
 
 class RangeErrorTest {
   static testRead() {
     testListRead([], 0);
     testListRead([], -1);
     testListRead([], 1);
 
     var list = [1];
     testListRead(list, -1);
@@ skipping 50 matching lines @@
     } on RangeError catch (e) {
       exception = e;
     }
     Expect.equals(true, exception != null);
   }
 }
 
 main() {
   RangeErrorTest.testMain();
 }