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

sdk/lib/io/secure_server_socket.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.
 
-part of "dart:io";
+part of dart.io;
 
 /**
  * The [SecureServerSocket] is a server socket, providing a stream of high-level
  * [Socket]s.
  *
  * See [SecureSocket] for more info.
  */
 class SecureServerSocket extends Stream<SecureSocket> {
   final RawSecureServerSocket _socket;
 
@@ skipping 266 matching lines @@
           onError: _controller.addError, onDone: _controller.close);
     } else {
       close();
     }
   }
 
   void set _owner(owner) {
     (_socket as dynamic)._owner = owner;
   }
 }