Fix warnings_checker.dart handling of multitests

tests/compiler/dart2js_extra/private_symbol_literal_test.dart

Index: tests/compiler/dart2js_extra/private_symbol_literal_test.dart
diff --git a/tests/compiler/dart2js_extra/private_symbol_literal_test.dart b/tests/compiler/dart2js_extra/private_symbol_literal_test.dart
index 31a278310e2901733b38735616af91a1005f9244..1f12b060934cfd38d3fbd64669f3438afd7d49d3 100644
--- a/tests/compiler/dart2js_extra/private_symbol_literal_test.dart
+++ b/tests/compiler/dart2js_extra/private_symbol_literal_test.dart
@@ -9,14 +9,14 @@ library symbol_literal_test;
 
 main() {
   print(#a);
-  print(#_a); /// 01: compile-time error
+  print(#_a); //# 01: compile-time error
 
   print(#a.b);
-  print(#_a.b); /// 02: compile-time error
-  print(#a._b); /// 03: compile-time error
+  print(#_a.b); //# 02: compile-time error
+  print(#a._b); //# 03: compile-time error
 
   print(#a.b.c);
-  print(#_a.b.c); /// 04: compile-time error
-  print(#a._b.c); /// 05: compile-time error
-  print(#a.b._c); /// 06: compile-time error
+  print(#_a.b.c); //# 04: compile-time error
+  print(#a._b.c); //# 05: compile-time error
+  print(#a.b._c); //# 06: compile-time error
 }