This photo opp is a very delibarate, calculated "in your face". It is Martin's and Bergoglio's answer to Chaput, Paprocki et al., who recently issued cautions about Martin's writings and speeches. The message here is that Martin is in good standing with the Pope and therefore, the Church...so watch your step boys, Francis has my back. We're Catholic, you are not.
Essentially, despite the smiley faces, this meeting and the photo is the Lavender Mafia flexing its muscles.
Keep in mind, Francis allowed no photos when he met Kim Davis, who refused to sign homo marriage certificates.