Make isEmpty a getter.

lib/html/templates/immutable_list_mixin.darttemplate

   // -- start List<$E> mixins.
   // $E is the element type.
 
   // From Iterable<$E>:
 
   Iterator<$E> iterator() {
     // Note: NodeLists are not fixed size. And most probably length shouldn't
     // be cached in both iterator _and_ forEach method. For now caching it
     // for consistency.
     return new _FixedSizeListIterator<$E>(this);
@@ skipping 23 matching lines @@
 
   Collection map(f($E element)) => _Collections.map(this, [], f);
 
   Collection<$E> filter(bool f($E element)) =>
      _Collections.filter(this, <$E>[], f);
 
   bool every(bool f($E element)) => _Collections.every(this, f);
 
   bool some(bool f($E element)) => _Collections.some(this, f);
 
-  bool isEmpty() => this.length == 0;
+  bool get isEmpty => this.length == 0;
 
   // From List<$E>:
 
   void sort([Comparator<$E> compare = Comparable.compare]) {
     throw new UnsupportedError("Cannot sort immutable List.");
   }
 
   int indexOf($E element, [int start = 0]) =>
       _Lists.indexOf(this, element, start, this.length);
 
@@ skipping 17 matching lines @@
   }
 
   void insertRange(int start, int rangeLength, [$E initialValue]) {
     throw new UnsupportedError("Cannot insertRange on immutable List.");
   }
 
   List<$E> getRange(int start, int rangeLength) =>
       _Lists.getRange(this, start, rangeLength, <$E>[]);
 
   // -- end List<$E> mixins.