fixes #150, broken code in js_number.dart

lib/runtime/dart/_interceptors.js

 var _interceptors;
 (function(exports) {
   'use strict';
   let JSArray = Array;
   let JSMutableArray$ = dart.generic(function(E) {
     class JSMutableArray extends JSArray$(E) {}
     JSMutableArray[dart.implements] = () => [JSMutableIndexable];
     return JSMutableArray;
   });
   let JSMutableArray = JSMutableArray$();
@@ skipping 187 matching lines @@
       if (result.codeUnitAt(dart.notNull(result.length) - 1) != rightParenCode) {
         return result;
       }
       return JSNumber._handleIEtoString(result);
     }
     static _handleIEtoString(result) {
       let match = /^([\da-z]+)(?:\.([\da-z]+))?\(e\+(\d+)\)$/.exec(result);
       if (match == null) {
         throw new core.UnsupportedError(`Unexpected toString result: ${result}`);
       }
-      let result = dart.dindex(match, 1);
+      result = dart.dindex(match, 1);
       let exponent = +dart.dindex(match, 3);
       if (dart.dindex(match, 2) != null) {
         result = result + dart.dindex(match, 2);
         exponent = dart.notNull(exponent) - dart.dindex(match, 2).length;
       }
       return dart.notNull(result) + core.String['*']("0", exponent);
     }
     toString() {
       if (dart.notNull(dart.equals(this, 0)) && 1 / this < 0) {
         return '-0.0';
@@ skipping 853 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 || (_interceptors = {}));