Remove Expect from core library.

tests/standalone/io/mime_multipart_parser_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";
 import 'dart:math';
 
 part "../../../sdk/lib/io/http_parser.dart";
 part "../../../sdk/lib/io/mime_multipart_parser.dart";
 
 void testParse(String message,
                String boundary,
                [List<Map> expectedHeaders,
                List expectedParts]) {
   _MimeMultipartParser parser;
@@ skipping 316 matching lines @@
 \r
 Body2\r
 --xxx\r\n""";
   Expect.throws(() => testParse(message, "xxx", null, [null, null]));
 }
 
 void main() {
   testParseValid();
   testParseInvalid();
 }