Let Dart code running in Sky add events to the trace timeline

sky/examples/stocks-fn/lib/stock_app.dart

Index: sky/examples/stocks-fn/lib/stock_app.dart
diff --git a/sky/examples/stocks-fn/lib/stock_app.dart b/sky/examples/stocks-fn/lib/stock_app.dart
index 0331b5233ad5f067ea059e0f49415f520535cb98..6ef1ba7f0ad497e741a61664ca1684e85abc5538 100644
--- a/sky/examples/stocks-fn/lib/stock_app.dart
+++ b/sky/examples/stocks-fn/lib/stock_app.dart
@@ -14,6 +14,7 @@ import 'package:sky/framework/components/popup_menu.dart';
 import 'package:sky/framework/components/scaffold.dart';
 import 'package:sky/framework/fn.dart';
 import 'package:sky/framework/theme/typography.dart' as typography;
+import 'package:sky/framework/tracing.dart';
 import 'stock_data.dart';
 import 'stock_list.dart';
 import 'stock_menu.dart';
@@ -42,7 +43,9 @@ class StocksApp extends App {
     fetchStockOracle().then((oracle) {
       setState(() {
         _sortedStocks = oracle.stocks;
-        _sortedStocks.sort((a, b) => a.symbol.compareTo(b.symbol));
+        trace('StocksApp::sortStocks', () {
+          _sortedStocks.sort((a, b) => a.symbol.compareTo(b.symbol));
+        });
       });
     });
   }