SDK fixes

test/dart_codegen/expect/convert/line_splitter.dart

 part of dart.convert;
  class LineSplitter extends Converter<String, List<String>> {const LineSplitter();
  List<String> convert(String data) {
   var lines = new List<String>();
    _LineSplitterSink._addSlice(data, 0, data.length, true, lines.add);
    return lines;
   }
- StringConversionSink startChunkedConversion(Sink<String> sink) {
+ StringConversionSink startChunkedConversion(Sink<dynamic> sink) {
   if (sink is! StringConversionSink) {
-    sink = new StringConversionSink.from(sink);
+    sink = new StringConversionSink.from(DEVC$RT.cast(sink, DEVC$RT.type((Sink<dynamic> _) {
+      }
+    ), DEVC$RT.type((Sink<String> _) {
+      }
+    ), "CompositeCast", """line 24, column 44 of dart:convert/line_splitter.dart: """, sink is Sink<String>, false));
     }
-   return new _LineSplitterSink(DEVC$RT.cast(sink, DEVC$RT.type((Sink<String> _) {
+   return new _LineSplitterSink(DEVC$RT.cast(sink, DEVC$RT.type((Sink<dynamic> _) {
     }
   ), StringConversionSink, "ImplicitCast", """line 26, column 34 of dart:convert/line_splitter.dart: """, sink is StringConversionSink, true));
   }
 }
  class _LineSplitterSink extends StringConversionSinkBase {static const int _LF = 10;
  static const int _CR = 13;
  final StringConversionSink _sink;
  String _carry;
  _LineSplitterSink(this._sink);
  void addSlice(String chunk, int start, int end, bool isLast) {
@@ skipping 41 matching lines @@
    if (isLast) {
     adder(carry);
     }
    else {
     return carry;
     }
   }
  return null;
 }
 }