When marking a FileUploadField readonly, the text field it uses for the path is marked readonly, but the button can still be clicked.
  1. Create the field, and add it to the page:
    Code:
    FileUploadField field = new FileUploadField();
    field.setReadOnly(true);
    formPanel.add(field);
  2. Click the 'Browse...' button
Expected behavior: nothing should happen
Actual behavior: file window