fixes #415, correct type for map literals

lib/runtime/dart/convert.js

Index: lib/runtime/dart/convert.js
diff --git a/lib/runtime/dart/convert.js b/lib/runtime/dart/convert.js
index 9dfc0715261733a7207b0f7ceff26bd40921901b..793575dba6598d6b1794ca768b14da5a0f71eaf7 100644
--- a/lib/runtime/dart/convert.js
+++ b/lib/runtime/dart/convert.js
@@ -631,7 +631,7 @@ dart_library.library('dart/convert', null, /* Imports */[
   let _FusedConverter = _FusedConverter$();
   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});
+      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(_) {}
   });