fixes #193, factory constructors as static methods

lib/runtime/dart/_interceptors.js

 var _interceptors = dart.defineLibrary(_interceptors, {});
 var core = dart.import(core);
 var _js_helper = dart.lazyImport(_js_helper);
 var _internal = dart.import(_internal);
 var _foreign_helper = dart.import(_foreign_helper);
 var _js_embedded_names = dart.import(_js_embedded_names);
 (function(exports, core, _js_helper, _internal, _foreign_helper, _js_embedded_names) {
   'use strict';
   let JSArray = Array;
   let JSMutableArray$ = dart.generic(function(E) {
@@ skipping 967 matching lines @@
     constructors: () => ({_CodeUnits: [_CodeUnits, [core.String]]}),
     methods: () => ({[core.$get]: [core.int, [core.int]]})
   });
   function _symbolToString(symbol) {
     return _internal.Symbol.getName(dart.as(symbol, _internal.Symbol));
   }
   dart.fn(_symbolToString, core.String, [core.Symbol]);
   function _symbolMapToStringMap(map) {
     if (map == null)
       return null;
-    let result = new (core.Map$(core.String, core.Object))();
+    let result = core.Map$(core.String, core.Object).new();
     map.forEach(dart.fn((key, value) => {
       result.set(_symbolToString(key), value);
     }, core.Object, [core.Symbol, core.Object]));
     return result;
   }
   dart.fn(_symbolMapToStringMap, core.Object, [core.Map$(core.Symbol, core.Object)]);
   function getInterceptor(object) {
     return void 0;
   }
   dart.fn(getInterceptor);
@@ skipping 214 matching lines @@
   exports.findInterceptorForType = findInterceptorForType;
   exports.JSBool = JSBool;
   exports.JSNull = JSNull;
   exports.JSIndexable = JSIndexable;
   exports.JSMutableIndexable = JSMutableIndexable;
   exports.JSObject = JSObject;
   exports.JavaScriptObject = JavaScriptObject;
   exports.PlainJavaScriptObject = PlainJavaScriptObject;
   exports.UnknownJavaScriptObject = UnknownJavaScriptObject;
 })(_interceptors, core, _js_helper, _internal, _foreign_helper, _js_embedded_names);