fixes #147, add more cases to isStateless

lib/runtime/dart/convert.js

 var convert;
 (function(exports) {
   'use strict';
   let ASCII = dart.const(new AsciiCodec());
   let _ASCII_MASK = 127;
   let _allowInvalid = Symbol('_allowInvalid');
   let Codec$ = dart.generic(function(S, T) {
     class Codec extends core.Object {
       Codec() {
       }
@@ skipping 1557 matching lines @@
       if (isLast)
         this.close();
     }
     add(str) {
       return this[_stringSink].write(str);
     }
     asUtf8Sink(allowMalformed) {
       return new _Utf8StringSinkAdapter(this, this[_stringSink], allowMalformed);
     }
     asStringSink() {
-      return new ClosableStringSink.fromStringSink(this[_stringSink], dart.bind(this, 'close'));
+      return new ClosableStringSink.fromStringSink(this[_stringSink], this.close.bind(this));
     }
   }
   class _StringCallbackSink extends _StringSinkConversionSink {
     _StringCallbackSink(callback) {
       this[_callback] = callback;
       super._StringSinkConversionSink(new core.StringBuffer());
     }
     close() {
       let buffer = dart.as(this[_stringSink], core.StringBuffer);
       let accumulated = dart.toString(buffer);
@@ skipping 828 matching lines @@
   exports.LineSplitter = LineSplitter;
   exports.StringConversionSink = StringConversionSink;
   exports.ClosableStringSink = ClosableStringSink;
   exports.UNICODE_REPLACEMENT_CHARACTER_RUNE = UNICODE_REPLACEMENT_CHARACTER_RUNE;
   exports.UNICODE_BOM_CHARACTER_RUNE = UNICODE_BOM_CHARACTER_RUNE;
   exports.UTF8 = UTF8;
   exports.Utf8Codec = Utf8Codec;
   exports.Utf8Encoder = Utf8Encoder;
   exports.Utf8Decoder = Utf8Decoder;
 })(convert || (convert = {}));