place_tracker: use_key_in_widget_constructors and Runners rebuild (#829)

place_tracker/lib/main.dart

@@ -10,6 +10,6 @@ import 'place_tracker_app.dart';
 void main() {
   runApp(ChangeNotifierProvider(
     create: (context) => AppState(),
-    child: PlaceTrackerApp(),
+    child: const PlaceTrackerApp(),
   ));
 }

place_tracker/lib/place_tracker_app.dart

@@ -17,6 +17,8 @@ enum PlaceTrackerViewType {
 }
 
 class PlaceTrackerApp extends StatelessWidget {
+  const PlaceTrackerApp({Key key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     return const MaterialApp(