Merge pull request #390 from abarth/fix_analyzer

Fix Dart analyzer warnings

Author: eseidelGoogle

sky/packages/sky/example/game/lib/game_demo.dart

@@ -9,6 +9,4 @@ import 'package:sky/widgets/widget.dart';
 import 'package:sky/widgets/navigator.dart';
 import 'package:vector_math/vector_math_64.dart';
 
-import '../main.dart';
-
 part 'game_demo_world.dart';

sky/packages/sky/lib/widgets/dismissable.dart

@@ -167,7 +167,7 @@ class Dismissable extends AnimatedComponent {
       _dragUnderway = false;
       _dragX = event.velocityX.sign;
       _position.end = _activeCardDragEndPoint;
-      _fadePerformance.fling(velocity: event.velocityX.abs() * _kFlingVelocityScale);
+      _fadePerformance.fling(Direction.forward, velocity: event.velocityX.abs() * _kFlingVelocityScale);
     }
   }