Make popup menus line up to their baseline per the Material spec.

sky/sdk/example/stocks/lib/stock_menu.dart

Index: sky/sdk/example/stocks/lib/stock_menu.dart
diff --git a/sky/sdk/example/stocks/lib/stock_menu.dart b/sky/sdk/example/stocks/lib/stock_menu.dart
index 4fb0e0d8808811b6cc6fd54f8ac2fa2d58ef90c5..9fc5721f5d5308138a4e24ef13a142ae0c5f8e6f 100644
--- a/sky/sdk/example/stocks/lib/stock_menu.dart
+++ b/sky/sdk/example/stocks/lib/stock_menu.dart
@@ -36,8 +36,8 @@ class StockMenu extends Component {
         ],
         level: 4
       ),
-      right: 8.0,
-      top: 8.0 + kStatusBarHeight
+      right: 0.0,
+      top: 0.0 + kStatusBarHeight
     );
   }
 }