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

lib/components/swap.dart

 library x_swap;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:meta/meta.dart';
 import 'package:web_ui/web_ui.dart';
 import 'package:bot/bot.dart';
 import 'package:widget/effects.dart';
 import 'package:widget/widget.dart';
 
@@ skipping 33 matching lines @@
     final newActive = items[index];
     return showItem(newActive, effect: effect, duration: duration, effectTiming: effectTiming, hideEffect: hideEffect);
   }
 
   @override
   Future<bool> showItem(Element item, {ShowHideEffect effect, int duration, EffectTiming effectTiming, ShowHideEffect hideEffect}) {
     assert(items.contains(item));
 
     final oldActiveChild = activeItem;
     if(oldActiveChild == item) {
-      return new Future<bool>.immediate(true);
+      return new Future<bool>.value(true);
     }
 
     [oldActiveChild, item].forEach((e) => e.classes.remove(_dirClassPrev));
 
     oldActiveChild.classes.remove(_activeClass);
     oldActiveChild.classes.add(_dirClassPrev);
 
     item.classes.add(_activeClass);
 
     return Swapper.swap(_contentElement, item, effect: effect, duration: duration, effectTiming: effectTiming, hideEffect: hideEffect)
@@ skipping 12 matching lines @@
     _contentElementField = null;
   }
 
   Element get _contentElement {
     _initialize();
     return _contentElementField;
   }
 
   void _initialize() {
     if(_contentElementField == null) {
-      _contentElementField = this.query('x-swap > .content');
+      _contentElementField = this.query('[is=x-swap] > .content');
       if(_contentElementField == null) {
         throw 'Could not find the content element. Either the template has changed or state was accessed too early in the component lifecycle.';
       }
 
       final theItems = _contentElementField.children;
 
       // if there are any elements, make sure one and only one is 'active'
       final activeFigures = new List<Element>.from(theItems.where((e) => e.classes.contains(_activeClass)).toList());
       if(activeFigures.length == 0) {
         if(theItems.length > 0) {
           // marke the first of the figures as active
           theItems[0].classes.add(_activeClass);
         }
       } else {
         activeFigures.sublist(1)
           .forEach((e) => e.classes.remove(_activeClass));
       }
 
       // A bit of a hack. Because we call Swap w/ two displayed items:
       // one marked 'prev' and one marked 'next', Swap tries to hide one of them
       // this only causes a problem when clicking right the first time, since all
       // times after, the cached ShowHideState of the item is set
       // So...we're going to walk the showHide states of all children now
       // ...and ignore the result...but just to populate the values
       theItems.forEach((f) => ShowHide.getState(f));
     }
   }
 }