Fix warnings_checker.dart handling of multitests

tests/compiler/dart2js/warnings_checker.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Test that dart2js produces the expected static type warnings to ensures that
 // the analyzer and dart2js agrees on the tests.
 
 import 'dart:async';
 import 'dart:io';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'memory_compiler.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/io/source_file.dart';
 import 'package:compiler/src/source_file_provider.dart';
 import 'package:compiler/src/util/uri_extras.dart';
 import 'dart:convert';
 
+final _multiTestRegExpSeperator = new RegExp(r"//[#/]");
+
 void checkWarnings(Map<String, dynamic> tests, [List<String> arguments]) {
   bool isWindows = Platform.isWindows;
   Uri script = currentDirectory.resolveUri(Platform.script);
   bool warningsMismatch = false;
   bool verbose = arguments != null && arguments.contains('-v');
   asyncTest(() => Future.forEach(tests.keys, (String test) async {
         Uri uri = script.resolve('../../$test');
         String source = UTF8.decode(readAll(uriPathToNative(uri.path)));
         SourceFile file = new StringSourceFile(
             uri, relativize(currentDirectory, uri, isWindows), source);
         Map<int, String> expectedWarnings = {};
         int lineNo = 0;
         for (String line in source.split('\n')) {
-          if (line.contains('///') &&
+          if (line.contains(_multiTestRegExpSeperator) &&
               (line.contains('static type warning') ||
                   line.contains('static warning'))) {
             expectedWarnings[lineNo] = line;
           }
           lineNo++;
         }
         Set<int> unseenWarnings = new Set<int>.from(expectedWarnings.keys);
         DiagnosticCollector collector = new DiagnosticCollector();
         await runCompiler(
             entryPoint: uri,
@@ skipping 31 matching lines @@
               String line = expectedWarnings[lineNo];
               print('$uri [${lineNo+1}]: Missing static type warning.');
               print(line);
             }
           }
         }
       }).then((_) {
         Expect.isFalse(warningsMismatch);
       }));
 }