Remove Expect from core library.

tests/language/optimized_string_charcodeat_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";
+
 // Test optimized charCodeAt and array access.
 
 String one_byte = "hest";
 String two_byte = "høns";
 
 int testOneByteCharCodeAt(String x, int i) {
   int test() {
     return x.charCodeAt(i);
   }
   for (int i = 0; i < 10000; i++) test();
@@ skipping 27 matching lines @@
   return test();
 }
 
 
 main() {
   Expect.equals(101, testOneByteCharCodeAt(one_byte, 1));
   Expect.equals(248, testTwoByteCharCodeAt(two_byte, 1));
   Expect.equals(248, testConstantStringCharCodeAt(1));
   Expect.equals(101, testConstantIndexCharCodeAt(one_byte));
 }