Fix warnings_checker.dart handling of multitests

tests/lib/async/run_zoned9_test.dart

Index: tests/lib/async/run_zoned9_test.dart
diff --git a/tests/lib/async/run_zoned9_test.dart b/tests/lib/async/run_zoned9_test.dart
index 9c07b4b525e59bb0fc3b05bc55a679eca57a2226..3d5dc80b5f161a506e6d308d9593712b4edbe07e 100644
--- a/tests/lib/async/run_zoned9_test.dart
+++ b/tests/lib/async/run_zoned9_test.dart
@@ -23,13 +23,13 @@ main() {
       Expect.equals(0, e);
       Expect.isTrue(sawInnerHandler);
       // If we are waiting for an error, don't asyncEnd, but let it time out.
-      if (false) /// 01: runtime error
+      if (false) //# 01: runtime error
         asyncEnd();
-      throw e; //  /// 01: continued
+      throw e; //  //# 01: continued
     });
   } catch (e) {
     // We should never see an error here.
-    if (false) //  /// 01: continued
+    if (false) //  //# 01: continued
       rethrow;
   }
 }