Delete all cookies that match the specified parameters. If both |url| and |cookie_name| values are specified all host and domain cookies matching both will be deleted. If only |url| is specified all host cookies (but not domain cookies) irrespective of path will be deleted. If |url| is NULL all cookies for all hosts and domains will be deleted. If |callback| is non- NULL it will be executed asnychronously on the UI thread after the cookies have been deleted. Returns false (0) if a non-NULL invalid URL is specified or if cookies cannot be accessed. Cookies can alternately be deleted using the Visit*Cookies() functions.