anchor.diff:  import '../exception.dart';
   import '../file_operations.dart';
   import '../objectstore.dart';
  +import '../permissions.dart';
   import '../utils.dart';
   
   /**
  
positive.code: class FileStatus {
    String path;
    String headSha;
    String sha;
    int size;
    bool deleted = false;
  
negative.code:    }
  
     Future _updateSha(chrome.FileEntry entry) {
       FileStatus status = _statusIdx[entry.fullPath];
       return entry.getMetadata().then((data) {
         if (status.modificationTime == data.modificationTime.millisecondsSinceEpoch) {
           return new Future.value();
         } else {
           return getShaForEntry(entry, 'blob').then((String sha) {
             FileStatus newStatus = new FileStatus()
                 ..sha = sha
                 ..path = status.path
                 ..size = data.size
                 ..modificationTime = data.modificationTime.millisecondsSinceEpoch
                 ..permission = status.permission;
             updateIndexForFile(newStatus);
           });
         }
       });
  