Fix warnings_checker.dart handling of multitests

tests/language/async_return_types_test.dart

Index: tests/language/async_return_types_test.dart
diff --git a/tests/language/async_return_types_test.dart b/tests/language/async_return_types_test.dart
index f8d194da0ce7649a0a34d764de2f681a7faa00b3..6cbd7faacd1bcd96169533cf62ad38be2b743dc5 100644
--- a/tests/language/async_return_types_test.dart
+++ b/tests/language/async_return_types_test.dart
@@ -14,18 +14,18 @@ Future<int> foo2() async {
   return 3;
 }
 
-Future<int> /// wrongTypeParameter: static type warning, dynamic type error
+Future<int> //# wrongTypeParameter: static type warning, dynamic type error
 foo3() async {
   return "String";
 }
 
 // Future<int, String> is treated like Future<dynamic>
-Future<int, String> /// tooManyTypeParameters: static type warning
+Future<int, String> //# tooManyTypeParameters: static type warning
 foo4() async {
   return "String";
 }
 
-int /// wrongReturnType: static type warning, dynamic type error
+int //# wrongReturnType: static type warning, dynamic type error
 foo5() async {
   return 3;
 }
@@ -35,7 +35,7 @@ Future<int> foo6() async {
   return new Future<int>.value(3);
 }
 
-Future<Future<int>> /// nestedFuture: static type warning, dynamic type error
+Future<Future<int>> //# nestedFuture: static type warning, dynamic type error
 foo7() async {
   return new Future<int>.value(3);
 }
@@ -45,7 +45,7 @@ Iterable<int> foo8() sync* {
   yield 1;
   // Can only have valueless return in sync* functions.
   return
-      8 /// return_value_sync_star: compile-time error
+      8 //# return_value_sync_star: compile-time error
        ;
 }
 
@@ -53,7 +53,7 @@ Stream<int> foo9() async* {
   yield 1;
   // Can only have valueless return in async* functions.
   return
-      8 /// return_value_sync_star: compile-time error
+      8 //# return_value_sync_star: compile-time error
        ;
 }