Support for 'async' in the old formatter.

pkg/analyzer/test/services/data/cu_tests.data

Index: pkg/analyzer/test/services/data/cu_tests.data
diff --git a/pkg/analyzer/test/services/data/cu_tests.data b/pkg/analyzer/test/services/data/cu_tests.data
index 06dddeff57b72e00e76976a1380f927ac29212af..6f4e4d1bfa18115077d1f05c325c28e484792406 100644
--- a/pkg/analyzer/test/services/data/cu_tests.data
+++ b/pkg/analyzer/test/services/data/cu_tests.data
@@ -307,3 +307,13 @@ class A {
   A(this.a0123456789012345678901234, this.b0123456789012345678901234,
       this.c0123456789012345678901234, this.d0123456789012345678901234);
 }
+>>>
+main() async {
+}
+<<<
+main() async {
+}
+>>>
+main()  async  => 0;
+<<<
+main() async => 0;