Avoid runtime type errors in checked mode for ChunkedConverters.

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;
 
 // Character constants.
 const int _LF = 10;
 const int _CR = 13;
 
 /**
  * A [Converter] 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),
  * and a final non-empty line can be ended by the end of the string.
  *
  * The returned lines do not contain the line terminators.
  */
 class LineSplitter
     extends Converter<String, List<String>>/*=Object*/
-    implements Object/*=StreamTransformer<String, String>*/ {
+    implements ChunkedConverter<String, List<String>, String, String>
+        /*=StreamTransformer<String, String>*/ {
 
   const LineSplitter();
 
   /// Split [lines] into individual lines.
   ///
   /// If [start] and [end] are provided, only split the contents of
   /// `lines.substring(start, end)`. The [start] and [end] values must
   /// specify a valid sub-range of [lines]
   /// (`0 <= start <= end <= lines.length`).
   static Iterable<String> split(String lines, [int start = 0, int end]) sync* {
@@ skipping 137 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);
   }
 }