We should use UserID object to identify users instead of username.

chrome/browser/chromeos/extensions/file_manager/private_api_drive.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/extensions/file_manager/private_api_drive.h"
 
 #include <map>
 #include <set>
 
 #include "base/command_line.h"
@@ skipping 963 matching lines @@
       role = google_apis::drive::PERMISSION_ROLE_COMMENTER;
       break;
     case api::file_manager_private::DRIVE_SHARE_TYPE_CAN_VIEW:
       role = google_apis::drive::PERMISSION_ROLE_READER;
       break;
   }
 
   // Share |drive_path| in |owner_file_system| to |user->email()|.
   owner_file_system->AddPermission(
       drive_path,
-      user->email(),
+      user->GetUserID(),
       role,
       base::Bind(&FileManagerPrivateRequestDriveShareFunction::OnAddPermission,
                  this));
   return true;
 }
 
 void FileManagerPrivateRequestDriveShareFunction::OnAddPermission(
     drive::FileError error) {
   SendResponse(error == drive::FILE_ERROR_OK);
 }
@@ skipping 82 matching lines @@
   }
 
   const std::string url =
       download_url_.Resolve("?access_token=" + access_token).spec();
   SetResult(new base::StringValue(url));
 
   SendResponse(true);
 }
 
 }  // namespace extensions