allow JS builtin to be typed as needed

lib/runtime/dart/core.js

 dart_library.library('dart/core', null, /* Imports */[
   'dart/_runtime'
 ], /* Lazy imports */[
   'dart/_js_helper',
   'dart/_internal',
   'dart/collection',
   'dart/_interceptors',
   'dart/convert'
 ], function(exports, dart, _js_helper, _internal, collection, _interceptors, convert) {
   'use strict';
@@ skipping 1340 matching lines @@
     class List extends Object {
       static new(length) {
         if (length === void 0) length = null;
         let list = null;
         if (length == null) {
           list = [];
         } else {
           if (!(typeof length == 'number') || dart.notNull(length) < 0) {
             dart.throw(new ArgumentError(`Length must be a non-negative integer: ${length}`));
           }
-          list = _interceptors.JSArray.markFixedList(dart.as(new Array(length), List$()));
+          list = _interceptors.JSArray.markFixedList(new Array(length));
         }
         return _interceptors.JSArray$(E).typed(list);
       }
       static filled(length, fill) {
         let result = List$(E).new(length);
         if (length != 0 && fill != null) {
           for (let i = 0; dart.notNull(i) < dart.notNull(result[dartx.length]); i = dart.notNull(i) + 1) {
             result[dartx.set](i, fill);
           }
         }
@@ skipping 1866 matching lines @@
   exports.StackTrace = StackTrace;
   exports.Stopwatch = Stopwatch;
   exports.String = String;
   exports.RuneIterator = RuneIterator;
   exports.StringBuffer = StringBuffer;
   exports.StringSink = StringSink;
   exports.Symbol = Symbol;
   exports.Type = Type;
   exports.Uri = Uri;
 });