a few small refactorings to closure workarounds

lib/runtime/dart/convert.js

 dart_library.library('dart/convert', null, /* Imports */[
   'dart/_runtime',
   'dart/core',
   'dart/async',
   'dart/typed_data',
   'dart/_internal',
   'dart/collection'
 ], /* Lazy imports */[
 ], function(exports, dart, core, async, typed_data, _internal, collection) {
   'use strict';
   let dartx = dart.dartx;
+  const _allowInvalid = Symbol('_allowInvalid');
   const Codec$ = dart.generic(function(S, T) {
     class Codec extends core.Object {
       Codec() {
       }
       encode(input) {
         dart.as(input, S);
         return this.encoder.convert(input);
       }
       decode(encoded) {
         dart.as(encoded, T);
@@ skipping 39 matching lines @@
     methods: () => ({decodeStream: [async.Future$(core.String), [async.Stream$(core.List$(core.int))]]}),
     statics: () => ({getByName: [Encoding, [core.String]]}),
     names: ['getByName']
   });
   dart.defineLazyProperties(Encoding, {
     get _nameToEncoding() {
       return dart.map({"iso_8859-1:1987": LATIN1, "iso-ir-100": LATIN1, "iso_8859-1": LATIN1, "iso-8859-1": LATIN1, latin1: LATIN1, l1: LATIN1, ibm819: LATIN1, cp819: LATIN1, csisolatin1: LATIN1, "iso-ir-6": ASCII, "ansi_x3.4-1968": ASCII, "ansi_x3.4-1986": ASCII, "iso_646.irv:1991": ASCII, "iso646-us": ASCII, "us-ascii": ASCII, us: ASCII, ibm367: ASCII, cp367: ASCII, csascii: ASCII, ascii: ASCII, csutf8: UTF8, "utf-8": UTF8}, core.String, Encoding);
     },
     set _nameToEncoding(_) {}
   });
-  const _allowInvalid = Symbol('_allowInvalid');
   class AsciiCodec extends Encoding {
     AsciiCodec(opts) {
       let allowInvalid = opts && 'allowInvalid' in opts ? opts.allowInvalid : false;
       this[_allowInvalid] = allowInvalid;
       super.Encoding();
     }
     get name() {
       return "us-ascii";
     }
     decode(bytes, opts) {
@@ skipping 11 matching lines @@
     get decoder() {
       return dart.notNull(this[_allowInvalid]) ? dart.const(new AsciiDecoder({allowInvalid: true})) : dart.const(new AsciiDecoder({allowInvalid: false}));
     }
   }
   dart.setSignature(AsciiCodec, {
     constructors: () => ({AsciiCodec: [AsciiCodec, [], {allowInvalid: core.bool}]}),
     methods: () => ({decode: [core.String, [core.List$(core.int)], {allowInvalid: core.bool}]})
   });
   const ASCII = dart.const(new AsciiCodec());
   const _ASCII_MASK = 127;
+  const _subsetMask = Symbol('_subsetMask');
   const Converter$ = dart.generic(function(S, T) {
     class Converter extends core.Object {
       Converter() {
       }
       fuse(other) {
         dart.as(other, Converter$(T, dart.dynamic));
         return new (_FusedConverter$(S, T, dart.dynamic))(this, other);
       }
       startChunkedConversion(sink) {
         dart.as(sink, core.Sink$(T));
         dart.throw(new core.UnsupportedError(`This converter does not support chunked conversions: ${this}`));
       }
       bind(source) {
         dart.as(source, async.Stream$(S));
         return async.Stream$(T).eventTransformed(source, dart.fn(sink => new _ConverterStreamEventSink(this, sink), _ConverterStreamEventSink, [async.EventSink]));
       }
     }
     Converter[dart.implements] = () => [async.StreamTransformer$(S, T)];
     dart.setSignature(Converter, {
       constructors: () => ({Converter: [Converter$(S, T), []]}),
       methods: () => ({
         fuse: [Converter$(S, dart.dynamic), [Converter$(T, dart.dynamic)]],
         startChunkedConversion: [ChunkedConversionSink, [core.Sink$(T)]],
         bind: [async.Stream$(T), [async.Stream$(S)]]
       })
     });
     return Converter;
   });
   let Converter = Converter$();
-  const _subsetMask = Symbol('_subsetMask');
   class _UnicodeSubsetEncoder extends Converter$(core.String, core.List$(core.int)) {
     _UnicodeSubsetEncoder(subsetMask) {
       this[_subsetMask] = subsetMask;
       super.Converter();
     }
     convert(string, start, end) {
       if (start === void 0) start = 0;
       if (end === void 0) end = null;
       let stringLength = string[dartx.length];
       core.RangeError.checkValidRange(start, end, stringLength);
@@ skipping 28 matching lines @@
     })
   });
   class AsciiEncoder extends _UnicodeSubsetEncoder {
     AsciiEncoder() {
       super._UnicodeSubsetEncoder(_ASCII_MASK);
     }
   }
   dart.setSignature(AsciiEncoder, {
     constructors: () => ({AsciiEncoder: [AsciiEncoder, []]})
   });
+  const _sink = Symbol('_sink');
   class StringConversionSinkMixin extends core.Object {
     add(str) {
       return this.addSlice(str, 0, str[dartx.length], false);
     }
     asUtf8Sink(allowMalformed) {
       return new _Utf8ConversionSink(this, allowMalformed);
     }
     asStringSink() {
       return new _StringConversionSinkAsStringSinkAdapter(this);
     }
   }
   StringConversionSinkMixin[dart.implements] = () => [StringConversionSink];
   dart.setSignature(StringConversionSinkMixin, {
     methods: () => ({
       add: [dart.void, [core.String]],
       asUtf8Sink: [ByteConversionSink, [core.bool]],
       asStringSink: [ClosableStringSink, []]
     })
   });
   class StringConversionSinkBase extends StringConversionSinkMixin {}
-  const _sink = Symbol('_sink');
   class _UnicodeSubsetEncoderSink extends StringConversionSinkBase {
     _UnicodeSubsetEncoderSink(subsetMask, sink) {
       this[_subsetMask] = subsetMask;
       this[_sink] = sink;
     }
     close() {
       this[_sink].close();
     }
     addSlice(source, start, end, isLast) {
       core.RangeError.checkValidRange(start, end, source[dartx.length]);
@@ skipping 78 matching lines @@
         return new _ErrorHandlingAsciiDecoderSink(stringSink.asUtf8Sink(false));
       } else {
         return new _SimpleAsciiDecoderSink(stringSink);
       }
     }
   }
   dart.setSignature(AsciiDecoder, {
     constructors: () => ({AsciiDecoder: [AsciiDecoder, [], {allowInvalid: core.bool}]}),
     methods: () => ({startChunkedConversion: [ByteConversionSink, [core.Sink$(core.String)]]})
   });
+  const _utf8Sink = Symbol('_utf8Sink');
   const ChunkedConversionSink$ = dart.generic(function(T) {
     class ChunkedConversionSink extends core.Object {
       ChunkedConversionSink() {
       }
       static withCallback(callback) {
         return new (_SimpleCallbackSink$(T))(callback);
       }
     }
     ChunkedConversionSink[dart.implements] = () => [core.Sink$(T)];
     dart.setSignature(ChunkedConversionSink, {
@@ skipping 28 matching lines @@
       super.ByteConversionSink();
     }
     addSlice(chunk, start, end, isLast) {
       this.add(chunk[dartx.sublist](start, end));
       if (dart.notNull(isLast)) this.close();
     }
   }
   dart.setSignature(ByteConversionSinkBase, {
     methods: () => ({addSlice: [dart.void, [core.List$(core.int), core.int, core.int, core.bool]]})
   });
-  const _utf8Sink = Symbol('_utf8Sink');
   class _ErrorHandlingAsciiDecoderSink extends ByteConversionSinkBase {
     _ErrorHandlingAsciiDecoderSink(utf8Sink) {
       this[_utf8Sink] = utf8Sink;
     }
     close() {
       this[_utf8Sink].close();
     }
     add(source) {
       this.addSlice(source, 0, source[dartx.length], false);
     }
@@ skipping 2469 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.Utf8Codec = Utf8Codec;
   exports.UTF8 = UTF8;
   exports.Utf8Encoder = Utf8Encoder;
   exports.Utf8Decoder = Utf8Decoder;
 });