Juan Leyva authored Oct 17, 2018 and Eloy Lafuente committed Oct 25, 2018

New method added block_base::get_content_for_external().
It will return all the block contents rendered for external functions.
If your block is returning formatted content or provide files for download,
you should override this method to use the external_format_text,
external_format_string functions for formatting or
external_util::get_area_files for files.
See block_html as example.