FileCache:
* Added FileCacheBase::*MissesRecent() functions for counting cache misses from different visitors.
* Made ObjectFileCache more generic.
* Cleaned up FileCacheBase::checkCacheDirs().
* Added FileCacheBase::typeSubdirectory() function and overwrote in HTMLFileCache. Fixes r98405 invalidating all existing cache due to directory change.
* Simplified FileCacheBase::checkCacheDirs() a bit
ResourceLoader:
* Use ResourceFileCache to handle load() requests, if $wgUseFileCache. Only caches requests for default language and skins. Single modules requests are always cached, whereas others require a certain threshold of traffic.
* Added ResourceFileCache class (functionality was initially to be in ObjectFileCache).