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

sdk/lib/convert/line_splitter.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:convert";
+part of dart.convert;
 
 // Character constants.
 const int _LF = 10;
 const int _CR = 13;
 
 /**
  * A [StreamTransformer] that splits a [String] into individual lines.
  *
  * A line is terminated by either a CR (U+000D), a LF (U+000A), a
  * CR+LF sequence (DOS line ending),
@@ skipping 153 matching lines @@
   final EventSink<String> _eventSink;
 
   _LineSplitterEventSink(EventSink<String> eventSink)
       : _eventSink = eventSink,
         super(new StringConversionSink.from(eventSink));
 
   void addError(Object o, [StackTrace stackTrace]) {
     _eventSink.addError(o, stackTrace);
   }
 }