I recently documented my experience in troubleshooting this frustrating issue on JIRA. The documentation is entirely wrong and it would save other developers/implementers/users a lot of time and headache if it was just removed or updated.
https://jira.dhis2.org/browse/DHIS2-7130
EDIT: I have resolved my issue and have succesffuly embedded some test charts. Feel free to contact me if you need assistance.