Don't call dinvoke on Object methods

test/dart_codegen/expect/convert/string_conversion.dart

 part of dart.convert;
  abstract class StringConversionSink extends ChunkedConversionSink<String> {StringConversionSink();
  factory StringConversionSink.withCallback(void callback(String accumulated)) = _StringCallbackSink;
  factory StringConversionSink.from(Sink<String> sink) = _StringAdapterSink;
  factory StringConversionSink.fromStringSink(StringSink sink) = _StringSinkConversionSink;
  void addSlice(String chunk, int start, int end, bool isLast);
  ByteConversionSink asUtf8Sink(bool allowMalformed);
  ClosableStringSink asStringSink();
 }
  abstract class ClosableStringSink extends StringSink {factory ClosableStringSink.fromStringSink(StringSink sink, void onClose()) = _ClosableStringSink;
@@ skipping 28 matching lines @@
 }
  void writeln([Object o = ""]) {
 _buffer.writeln(o);
  if (_buffer.length > _MIN_STRING_SIZE) _flush();
 }
  void writeAll(Iterable objects, [String separator = ""]) {
 if (_buffer.isNotEmpty) _flush();
  Iterator iterator = objects.iterator;
  if (!iterator.moveNext()) return; if (separator.isEmpty) {
 do {
-_chunkedSink.add(((__x15) => DEVC$RT.cast(__x15, dynamic, String, "DynamicCast", """line 147, column 26 of dart:convert/string_conversion.dart: """, __x15 is String, true))(iterator.current.toString()));
+_chunkedSink.add(iterator.current.toString());
 }
  while (iterator.moveNext());}
  else {
-_chunkedSink.add(((__x16) => DEVC$RT.cast(__x16, dynamic, String, "DynamicCast", """line 150, column 24 of dart:convert/string_conversion.dart: """, __x16 is String, true))(iterator.current.toString()));
+_chunkedSink.add(iterator.current.toString());
  while (iterator.moveNext()) {
 write(separator);
- _chunkedSink.add(((__x17) => DEVC$RT.cast(__x17, dynamic, String, "DynamicCast", """line 153, column 26 of dart:convert/string_conversion.dart: """, __x17 is String, true))(iterator.current.toString()));
+ _chunkedSink.add(iterator.current.toString());
 }
 }
 }
  void _flush() {
 String accumulated = _buffer.toString();
  _buffer.clear();
  _chunkedSink.add(accumulated);
 }
 }
  abstract class StringConversionSinkBase extends StringConversionSinkMixin {}
@@ skipping 93 matching lines @@
  void addSlice(List<int> chunk, int startIndex, int endIndex, bool isLast) {
 _decoder.convert(chunk, startIndex, endIndex);
  if (_buffer.isNotEmpty) {
 String accumulated = _buffer.toString();
  _chunkedSink.addSlice(accumulated, 0, accumulated.length, isLast);
  _buffer.clear();
  return;}
  if (isLast) close();
 }
 }