Run dartfmt on kernel package

pkg/kernel/testcases/input/void-methods.dart

Index: pkg/kernel/testcases/input/void-methods.dart
diff --git a/pkg/kernel/testcases/input/void-methods.dart b/pkg/kernel/testcases/input/void-methods.dart
index 36f4e72735d6edbd37a14de25a79cdfd50627ad2..2d847fa3d781367725dfd0bf2d14368c1689a598 100644
--- a/pkg/kernel/testcases/input/void-methods.dart
+++ b/pkg/kernel/testcases/input/void-methods.dart
@@ -1,7 +1,7 @@
 class Foo {
-  List list = [1,2,3];
+  List list = [1, 2, 3];
   set first(x) => list[0] = x;
-  operator[]=(x,y) => list[x] = y;
+  operator []=(x, y) => list[x] = y;
   void clear() => list.clear();
 }