The definition of a button for submitting the file in a file upload input.
This class is not really part of the API. It just illustrates the properties
that developers can use to define and create a button for submitting the file in a file upload input.
Once the dialog is opened, the created element becomes a CKEDITOR.ui.dialog.fileButton object
and can be accessed with CKEDITOR.dialog.getContentElement.
For a complete example of dialog definition, please check CKEDITOR.dialog.add.
