Fix warnings_checker.dart handling of multitests

tests/language_strong/bad_raw_string_test.dart

Index: tests/language_strong/bad_raw_string_test.dart
diff --git a/tests/language_strong/bad_raw_string_test.dart b/tests/language_strong/bad_raw_string_test.dart
index 04bcb5499d6f67dd70206710344ecef54b378b95..855f747e4cc337f09fd7f1d9b435ceb756f93a0e 100644
--- a/tests/language_strong/bad_raw_string_test.dart
+++ b/tests/language_strong/bad_raw_string_test.dart
@@ -5,19 +5,19 @@
 main() {
   // Raw String may not contain newline (may not be multi-line).
   String x = ''
-    r' // /// 01: compile-time error
-' //      /// 01: continued
-    r" // /// 02: compile-time error
-" //      /// 02: continued
+    r' // //# 01: compile-time error
+' //      //# 01: continued
+    r" // //# 02: compile-time error
+" //      //# 02: continued
     // Test that a raw string containing just one character, a \n char, fails.
     // Enclose the test string in a bigger multiline string, except in case 03:
-    ''' // /// 03: compile-time error
+    ''' // //# 03: compile-time error
     """
-    ''' // /// 03: continued
+    ''' // //# 03: continued
     r'
 '
-    ''' // /// 03: continued
+    ''' // //# 03: continued
     """
-    ''' // /// 03: continued
+    ''' // //# 03: continued
   ;
 }