Function lend_content 

pub fn lend_content(store: Option<ContentStore>)

Let the windows this process draws read their content addresses from store: what a session lends the windows it draws in its own process, once it knows the store the workspaces’ content is read through. Until it is called a process the launcher handed no store of its own reads no content address.

The pictures keep the store they were built with, so what this changes is where their bytes come from, read afresh each time a picture is asked for. None forgets the loads that failed against no store, so the pictures drawn again are asked for afresh; a store already lent is left to the pictures’ own cache.