Handle the <source> subelements of <picture>, and also rewrite the srcset attribute that source elements have
Handle the <source> subelements of <picture>, and also rewrite the srcset attribute that source elements have

mozilla-services/pageshot,fzzzy/pageshot,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/screenshots,fzzzy/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/screenshots