Run dartfmt on kernel package

pkg/kernel/testcases/input/argument.dart

 abstract class Base {}
 
 class Foo extends Base {}
+
 class Bar extends Base {}
+
 class Baz extends Base {}
 
-void foo(x) {
+void foo(x) {}
 
-}
+void bar(x) {}
 
-void bar(x) {
+void foo_escaped(x) {}
 
-}
-
-void foo_escaped(x) {
-
-}
-
-void bar_escaped(x) {
-
-}
+void bar_escaped(x) {}
 
 void escape(fn) {
   fn(new Baz());
 }
 
 main() {
   foo(new Foo());
   bar(new Bar());
   escape(foo_escaped);
   escape(bar_escaped);
 }