Add more tested features to closure_test

tests/compiler/dart2js/annotated_code_helper.dart

 // Copyright (c) 2016, 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.
 
 const int _LF = 0x0A;
 const int _CR = 0x0D;
 const int _LBRACE = 0x7B;
 
 const Pattern atBraceStart = '@{';
 const Pattern braceEnd = '}';
 
-final Pattern commentStart = new RegExp(r' */\*');
+final Pattern commentStart = new RegExp(r'/\*');
 final Pattern commentEnd = new RegExp(r'\*/ *');
 
 class Annotation {
   /// 1-based line number of the annotation.
   final int lineNo;
 
   /// 1-based column number of the annotation.
   final int columnNo;
 
   /// 0-based character offset  of the annotation within the source text.
@@ skipping 138 matching lines @@
     int offset = 0;
     for (Annotation annotation in list) {
       sb.write(sourceCode.substring(offset, annotation.offset));
       sb.write('@{${annotation.text}}');
       offset = annotation.offset;
     }
     sb.write(sourceCode.substring(offset));
     return sb.toString();
   }
 }