contentcollector: Delete unnecessary `dom` functions
contentcollector: Delete unnecessary `dom` functions

And move the remaining functions out of the `makeContentCollector()`
function.

ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite