Fix warnings_checker.dart handling of multitests

tests/language/parameter_default_test.dart

Index: tests/language/parameter_default_test.dart
diff --git a/tests/language/parameter_default_test.dart b/tests/language/parameter_default_test.dart
index 9f279bbc55ed60f4ff266eb8079ee0f10ea632c8..6a00febd817ac04708fbd8ebd69b60aa793963f0 100644
--- a/tests/language/parameter_default_test.dart
+++ b/tests/language/parameter_default_test.dart
@@ -4,25 +4,25 @@
 
 class C {
   foo(a
-      : 1 // /// 01: compile-time error
-      = 1 // /// 02: compile-time error
+      : 1 // //# 01: compile-time error
+      = 1 // //# 02: compile-time error
   ) { print(a); }
 
   static bar(a
-      : 1 // /// 03: compile-time error
-      = 1 // /// 04: compile-time error
+      : 1 // //# 03: compile-time error
+      = 1 // //# 04: compile-time error
   ) { print(a); }
 }
 
 baz(a
-    : 1 // /// 05: compile-time error
-    = 1 // /// 06: compile-time error
+    : 1 // //# 05: compile-time error
+    = 1 // //# 06: compile-time error
 ) { print(a); }
 
 main() {
   foo(a
-      : 1 // /// 07: compile-time error
-      = 1 // /// 08: compile-time error
+      : 1 // //# 07: compile-time error
+      = 1 // //# 08: compile-time error
   ) { print(a); }
 
   foo(1);