Make dart:convert strong mode clean.

sdk/lib/convert/line_splitter.dart

Index: sdk/lib/convert/line_splitter.dart
diff --git a/sdk/lib/convert/line_splitter.dart b/sdk/lib/convert/line_splitter.dart
index a9c94488a6c366e35d8650785403ef71338aac88..b728d8f2c2edf434a7e7f49f62216dc0451dec6c 100644
--- a/sdk/lib/convert/line_splitter.dart
+++ b/sdk/lib/convert/line_splitter.dart
@@ -17,8 +17,9 @@ const int _CR = 13;
  *
  * The returned lines do not contain the line terminators.
  */
-class LineSplitter extends
-    ChunkedConverter<String, List<String>, String, String> {
+class LineSplitter
+    extends Converter<String, List<String>>/*=Object*/
+    implements Object/*=StreamTransformer<String, String>*/ {
 
   const LineSplitter();
 
@@ -80,6 +81,12 @@ class LineSplitter extends
     }
     return new _LineSplitterSink(sink);
   }
+
+  Stream/*<String>*/ bind(Stream/*<String>*/ stream) {
+    return new Stream<String>.eventTransformed(
+          stream,
+          (EventSink<String> sink) => new _LineSplitterEventSink(sink));
+  }
 }
 
 // TODO(floitsch): deal with utf8.
@@ -157,3 +164,16 @@ class _LineSplitterSink extends StringConversionSinkBase {
     }
   }
 }
+
+class _LineSplitterEventSink extends _LineSplitterSink
+    implements EventSink<String> {
+  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);
+  }
+}