fixes #157, renaming local library identifiers if needed.

lib/runtime/dart/convert.js

-var convert;
-(function(exports) {
+var convert = dart.defineLibrary(convert, {});
+var core = dart.import(core);
+var async = dart.lazyImport(async);
+var typed_data = dart.lazyImport(typed_data);
+var _internal = dart.import(_internal);
+var collection = dart.import(collection);
+(function(exports, core, async, typed_data, _internal, collection) {
   '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() {
       }
       encode(input) {
         dart.as(input, S);
@@ skipping 2409 matching lines @@
   exports.Latin1Decoder = Latin1Decoder;
   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 = {}));
+})(convert, core, async, typed_data, _internal, collection);