Re-work MaterialComponent

sky/examples/stocks-fn/stockrow.dart

Index: sky/examples/stocks-fn/stockrow.dart
diff --git a/sky/examples/stocks-fn/stockrow.dart b/sky/examples/stocks-fn/stockrow.dart
index 71c1042bae1f995225aed8924f02d73ca5f30a5f..6eb9df648039df1e2b1914a16fdf5e35798ebe74 100644
--- a/sky/examples/stocks-fn/stockrow.dart
+++ b/sky/examples/stocks-fn/stockrow.dart
@@ -1,6 +1,6 @@
 part of stocksapp;
 
-class StockRow extends Material {
+class StockRow extends Component {
 
   Stock stock;
 
@@ -62,9 +62,7 @@ class StockRow extends Material {
       )
     ];
 
-    children.add(super.build());
-
-    return new Container(
+    return new Material(
       style: _style,
       children: children
     );