Revert "Change some platform libraries to use `part of URI`."

sdk/lib/io/socket.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.
 
-part of "dart:io";
+part of dart.io;
 
 /**
  * [InternetAddressType] is the type an [InternetAddress]. Currently,
  * IP version 4 (IPv4) and IP version 6 (IPv6) are supported.
  */
 class InternetAddressType {
   static const InternetAddressType IP_V4 = const InternetAddressType._(0);
   static const InternetAddressType IP_V6 = const InternetAddressType._(1);
   static const InternetAddressType ANY = const InternetAddressType._(-1);
 
@@ skipping 708 matching lines @@
     }
     if (address != null) {
       sb.write(", address = ${address.host}");
     }
     if (port != null) {
       sb.write(", port = $port");
     }
     return sb.toString();
   }
 }