Fix bad reference in city-list

sky/examples/city-list/city-list.sky

 <!--
 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 -->
 <import src="../../framework/sky-element/sky-element.sky" as="SkyElement" />
 <import src="city-data-service.sky" as="CityDataService" />
 <import src="city-sequence.sky" as="CitySequence" />
 
 <template>
@@ skipping 461 matching lines @@
       while (this.firstItem > 0 &&
              targetTop < this.drawTop) {
 
         var datum = data[this.firstItem - 1];
         var type = this.viewType(datum);
         var height = viewHeights[type];
 
         this.drawTop -= height;
 
         var tile = targetBottom < this.drawTop ?
-            new Tile(datum, null, viewType, -1) : // off-screen
+            new Tile(datum, null, datum.viewType, -1) : // off-screen
             this.checkoutTile(type, datum, this.drawTop);
 
         this.firstItem--;
         tiles.unshift(tile);
       }
 
       // Layout down to targetBottom
       while (this.firstItem + tiles.length < data.length - 1 &&
              targetBottom > this.drawBottom) {
 
         var datum = data[this.firstItem + tiles.length];
         var type = this.viewType(datum);
         var height = viewHeights[type];
 
         this.drawBottom += height;
 
         var tile = targetTop > this.drawBottom ?
-            new Tile(datum, null, viewType, -1) : // off-screen
+            new Tile(datum, null, datum.viewType, -1) : // off-screen
             this.checkoutTile(type, datum, this.drawBottom - height);
 
         tiles.push(tile);
       }
 
       // Debug validate:
       // for (var i = 0; i < tiles.length; i++) {
       //   if (tiles[i].datum !== data[this.firstItem + i])
       //     throw Error('Invalid')
       // }
@@ skipping 82 matching lines @@
           return;
 
         this.updateView(this.loader.getItems(), true);
       }
     });
 
 })(this);
 
 </script>