Fix warnings_checker.dart handling of multitests

tests/language_strong/not_enough_positional_arguments_test.dart

Index: tests/language_strong/not_enough_positional_arguments_test.dart
diff --git a/tests/language_strong/not_enough_positional_arguments_test.dart b/tests/language_strong/not_enough_positional_arguments_test.dart
index ea50a09702c5a132ebb01e3fea6debf0d93761c7..33cffcd1046c722bd4ea153ee58305445099d9fe 100644
--- a/tests/language_strong/not_enough_positional_arguments_test.dart
+++ b/tests/language_strong/not_enough_positional_arguments_test.dart
@@ -15,13 +15,13 @@ class A {
 
 class B {
   B()
-    : super.test(b: 1) // /// 01: runtime error
+    : super.test(b: 1) // //# 01: runtime error
   ;
 }
 
 class C extends A {
   C()
-    : super.test(b: 1) // /// 02: runtime error
+    : super.test(b: 1) // //# 02: runtime error
   ;
 }
 
@@ -32,16 +32,16 @@ class D {
 
 class E extends D {
   E()
-    : super.test(b: 1) // /// 05: runtime error
+    : super.test(b: 1) // //# 05: runtime error
   ;
 }
 
 main() {
-  new A.test(b: 1); // /// 00: runtime error
+  new A.test(b: 1); // //# 00: runtime error
   new B();
   new C();
-  new D.test(b: 1); // /// 03: runtime error
+  new D.test(b: 1); // //# 03: runtime error
   new E();
-  foo(b: 1); // /// 06: runtime error
-  bar(b: 1); // /// 07: runtime error
+  foo(b: 1); // //# 06: runtime error
+  bar(b: 1); // //# 07: runtime error
 }