samples/poppopwin: upgrade to first-class sample

samples/third_party/pop-pop-win/lib/src/poppopwin/game_state.dart

Index: samples/third_party/pop-pop-win/lib/src/poppopwin/game_state.dart
diff --git a/samples/third_party/pop-pop-win/lib/src/poppopwin/game_state.dart b/samples/third_party/pop-pop-win/lib/src/poppopwin/game_state.dart
deleted file mode 100644
index f17d09ac66b4ef6ade204955f04f32921f7ad337..0000000000000000000000000000000000000000
--- a/samples/third_party/pop-pop-win/lib/src/poppopwin/game_state.dart
+++ /dev/null
@@ -1,13 +0,0 @@
-part of ppw;
-
-class GameState {
-  static const GameState reset = const GameState._internal("reset");
-  static const GameState started = const GameState._internal("started");
-  static const GameState won = const GameState._internal("won");
-  static const GameState lost = const GameState._internal("lost");
-  final String name;
-
-  const GameState._internal(this.name);
-
-  String toString() => 'GameState: $name';
-}