Fix warnings_checker.dart handling of multitests

tests/language/super_operator_index_test.dart

Index: tests/language/super_operator_index_test.dart
diff --git a/tests/language/super_operator_index_test.dart b/tests/language/super_operator_index_test.dart
index 36c6819fee23652ed0f5e4bacb5f9fb13a81cedb..10b7a36c41bb088c606ca381df6d3c3607baf198 100644
--- a/tests/language/super_operator_index_test.dart
+++ b/tests/language/super_operator_index_test.dart
@@ -11,8 +11,8 @@ class A {
 class B extends A {
   foo() {
     super[4] = 42;
-    super[4] += 5; /// 01: static type warning, runtime error
-    return super[2]; /// 02: static type warning, runtime error
+    super[4] += 5; //# 01: static type warning, runtime error
+    return super[2]; //# 02: static type warning, runtime error
   }
 }
 
@@ -22,17 +22,17 @@ class C {
 
 class D extends C {
   foo() {
-    super[4] = 42; /// 03: static type warning, runtime error
-    super[4] += 5; /// 04: static type warning, runtime error
+    super[4] = 42; //# 03: static type warning, runtime error
+    super[4] += 5; //# 04: static type warning, runtime error
     return super[2];
   }
 }
 
 class E {
   foo() {
-    super[4] = 42; /// 05: static type warning, runtime error
-    super[4] += 5; /// 06: static type warning, runtime error
-    return super[2]; /// 07: static type warning, runtime error
+    super[4] = 42; //# 05: static type warning, runtime error
+    super[4] += 5; //# 06: static type warning, runtime error
+    return super[2]; //# 07: static type warning, runtime error
   }
 }