Fix widget.dart to work with the latest web_ui library. Specifically, query selectors need to use "…

build.dart

 import 'dart:async';
 import 'dart:io';
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/parser.dart';
 import 'package:html5lib/dom_parsing.dart';
 import 'package:web_ui/component_build.dart' as build_utils;
 import 'package:bot/bot.dart';
 
 final _whitespaceRegex = new RegExp(r'\s+');
 
@@ skipping 84 matching lines @@
 }
 
 Future<bool> _updateIfChanged(String filePath, String newContent) {
   final file = new File(filePath);
   return file.exists()
       .then((bool exists) {
         if(exists) {
           return file.readAsString()
               .then((String content) => content != newContent);
         } else {
-          return new Future.immediate(true);
+          return new Future.value(true);
         }
       }).then((bool shouldUpdate) {
         if(shouldUpdate) {
           return file.writeAsString(newContent)
             .then((_) => true);
         } else {
-          return new Future.immediate(false);
+          return new Future.value(false);
         }
       });
 }
 
 // TODO: crazy hack. Really need select recursive
 //       or propery query support...whichever
 List<Element> _findElements(Element element, Func1<Element, bool> predicate, [List<Element> target]) {
   if(target == null) {
     target = new List<Element>();
   }
@@ skipping 105 matching lines @@
   });
 
   for(var i = 0; i < lines.length; i++) {
     lines[i] = lines[i].substring(minPrefix);
   }
 
   input = lines.join('\n');
 
   return input;
 }