Multi-Content Revisions/Rendering and Caching


 * Typically, the rendering of one slot will be independent of other slots. It's produced by the  method of the slot's   object.
 * Some content models however may allow access to other slots (of the same revision, or of other pages), e.g. to render a wikitext infobox based on data stored separately from the wikitext.
 * To accommodate such access
 * should get the relevant RevisionRecord as an (optional?) parameter.
 * needs a  method, analogous to the   and   methods that similarly exist to provide context.


 * The  key will have to be based on the slot name as well as the page title.
 * The purging mechanism should also be per-slot.
 * The web cache will be for a rendering of all slots of the current revision. Single slot views using the  parameter will probably not need to be cached.