Fix warnings_checker.dart handling of multitests

tests/compiler/dart2js_extra/mirror_printer_test.dart

Index: tests/compiler/dart2js_extra/mirror_printer_test.dart
diff --git a/tests/compiler/dart2js_extra/mirror_printer_test.dart b/tests/compiler/dart2js_extra/mirror_printer_test.dart
index 8d6c129b739033ba165bf930e376399fd97ce7b5..9f5d5b7d3c062e2fb9f13dea0edd948f9af9fa45 100644
--- a/tests/compiler/dart2js_extra/mirror_printer_test.dart
+++ b/tests/compiler/dart2js_extra/mirror_printer_test.dart
@@ -20,7 +20,7 @@ import 'dart:mirrors';
 import 'crash_library_metadata.dart'; // This would crash dart2js.
 
 // Importing dart:html to make things interesting.
-import 'dart:html'; /// 01: ok
+import 'dart:html'; //# 01: ok
 
 class MirrorPrinter {
   final StringBuffer buffer;
@@ -185,5 +185,5 @@ main() {
   print(MirrorPrinter.stringify(currentMirrorSystem().libraries));
   // Clear the nodes to avoid confusing the fine test framework (by "fine" I
   // mean something else) -- ahe.
-  document.body.nodes.clear(); /// 01: continued
+  document.body.nodes.clear(); //# 01: continued
 }