Fix warnings_checker.dart handling of multitests

tests/language/mixin_illegal_super_use_test.dart

Index: tests/language/mixin_illegal_super_use_test.dart
diff --git a/tests/language/mixin_illegal_super_use_test.dart b/tests/language/mixin_illegal_super_use_test.dart
index fb5d70d29a52426bc5f19868eb1070d75a9840ab..e633ad1e2b479f25cf2dbc78a82bbc29b2cd5671 100644
--- a/tests/language/mixin_illegal_super_use_test.dart
+++ b/tests/language/mixin_illegal_super_use_test.dart
@@ -9,21 +9,21 @@ class M {
 
 class P0 {
   foo() {
-    super.toString(); //   /// 01: compile-time error
-    super.foo(); //        /// 02: compile-time error
-    super.bar = 100; //    /// 03: compile-time error
+    super.toString(); //   //# 01: compile-time error
+    super.foo(); //        //# 02: compile-time error
+    super.bar = 100; //    //# 03: compile-time error
 
     void inner() {
-      super.toString(); // /// 04: compile-time error
-      super.foo(); //      /// 05: compile-time error
-      super.bar = 100; //  /// 06: compile-time error
+      super.toString(); // //# 04: compile-time error
+      super.foo(); //      //# 05: compile-time error
+      super.bar = 100; //  //# 06: compile-time error
     }
     inner();
 
     (() {
-      super.toString(); // /// 07: compile-time error
-      super.foo(); //      /// 08: compile-time error
-      super.bar = 100; //  /// 09: compile-time error
+      super.toString(); // //# 07: compile-time error
+      super.foo(); //      //# 08: compile-time error
+      super.bar = 100; //  //# 09: compile-time error
     })();
 
     return 42;
@@ -32,7 +32,7 @@ class P0 {
 
 class P1 {
   bar() {
-    super.toString(); //   /// 10: compile-time error
+    super.toString(); //   //# 10: compile-time error
     return 87;
   }
 
@@ -52,7 +52,7 @@ class P1 {
 
 class P2 {
   baz() {
-    super.toString(); //  /// 11: compile-time error
+    super.toString(); //  //# 11: compile-time error
     return 99;
   }
 }