Merge pull request #680 from abarth/fix_analyzer

Add missing import to flutter_sprites

packages/flutter_sprites/lib/flutter_sprites.dart

@@ -18,6 +18,7 @@ import 'package:flutter/gestures.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 import 'package:vector_math/vector_math_64.dart';