[Effen] Prevent scrolling past the bottom of a scrollable list.

sky/examples/stocks/lib/stock_list.dart

Index: sky/examples/stocks/lib/stock_list.dart
diff --git a/sky/examples/stocks/lib/stock_list.dart b/sky/examples/stocks/lib/stock_list.dart
index 2e6e5bbf1d9db5e92f85d7b4edcb8dd200bc0f48..78a8d64c6b490c0c5962da26a99e2340dc0e9d67 100644
--- a/sky/examples/stocks/lib/stock_list.dart
+++ b/sky/examples/stocks/lib/stock_list.dart
@@ -16,12 +16,15 @@ class Stocklist extends FixedHeightScrollable {
     Object key,
     this.stocks,
     this.query
-  }) : super(key: key, scrollBehavior: new OverscrollBehavior());
+  }) : super(key: key);
 
   List<UINode> buildItems(int start, int count) {
-    return stocks
-      .where((stock) => query == null || stock.symbol.contains(
-          new RegExp(query, caseSensitive: false)))
+    var filteredStocks = stocks.where((stock) {
+      return query == null ||
+             stock.symbol.contains(new RegExp(query, caseSensitive: false));
+    });
+    itemCount = filteredStocks.length;

[abarth-chromium, 2015/06/04 16:23:17]

Won't this |length| query force the filter to be eagerly evaluated on the entire
list?  What if the list of stocks is very, very long?  Previously, this code
only needed to touch enough of the list to get the information visible in the
viewport.

+    return filteredStocks
       .skip(start)
       .take(count)
       .map((stock) => new StockRow(stock: stock))