Use relative URIs for core library part-of statements.

tests/standalone/io/web_socket_ping_test.dart

 // Copyright (c) 2013, 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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 library dart.io;
 
 import "package:expect/expect.dart";
 import "dart:async";
+import "dart:convert" show BASE64;
 import "dart:io";
 import "dart:math";
 
-part "../../../sdk/lib/io/crypto.dart";
+import "hash_utils.dart";
 
 const String webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 void testPing(int totalConnections) {
   HttpServer.bind('localhost', 0).then((server) {
     int closed = 0;
     server.listen((request) {
       var response = request.response;
       response.statusCode = HttpStatus.SWITCHING_PROTOCOLS;
       response.headers.set(HttpHeaders.CONNECTION, "upgrade");
       response.headers.set(HttpHeaders.UPGRADE, "websocket");
       String key = request.headers.value("Sec-WebSocket-Key");
-      _SHA1 sha1 = new _SHA1();
+      var sha1 = new SHA1();
       sha1.add("$key$webSocketGUID".codeUnits);
-      String accept = _CryptoUtils.bytesToBase64(sha1.close());
+      String accept = BASE64.encode(sha1.close());
       response.headers.add("Sec-WebSocket-Accept", accept);
       response.headers.contentLength = 0;
       response.detachSocket().then((socket) {
         socket.drain().then((_) {
           socket.close();
           closed++;
           if (closed == totalConnections) {
             server.close();
           }
         });
       });
     });
 
     for (int i = 0; i < totalConnections; i++) {
       WebSocket.connect('ws://localhost:${server.port}').then((webSocket) {
         webSocket.pingInterval = const Duration(milliseconds: 100);
         webSocket.drain();
       });
     }
   });
 }
 
 void main() {
   testPing(10);
 }