Merge "Convert SiteStatsUpdate to using getMainStashInstance()"

diff --cc includes/objectcache/ObjectCache.php
index 0912350,27d8802..217b61f
--- 1/includes/objectcache/ObjectCache.php
--- 2/includes/objectcache/ObjectCache.php
+++ b/includes/objectcache/ObjectCache.php
@@@ -56,17 -63,9 +56,17 @@@ use MediaWiki\Logger\LoggerFactory
   *   Purpose: Memory storage for per-cluster coordination and tracking.
   *   A typical use case would be a rate limit counter or cache regeneration mutex.
   *   Stored centrally within the local data-center. Not replicated to other DCs.
-  *   Also known as $wgMemc. Configured by $wgMainCacheType.
+  *   Configured by $wgMainCacheType.
   *
 - * - wfGetCache( $cacheType )
 + * - ObjectCache::getMainStashInstance()
 + *   Purpose: Ephemeral global storage.
 + *   Stored centrally within the primary data-center.
 + *   Changes are applied there first and replicated to other DCs (best-effort).
 + *   To retrieve the latest value (e.g. not from a slave), use BagOStuff:READ_LATEST.
 + *   This store may be subject to LRU style evictions.
 + *
 + * - ObjectCache::getInstance( $cacheType )
 + *   Purpose: Special cases (like tiered memory/disk caches).
   *   Get a specific cache type by key in $wgObjectCaches.
   *
   * All the above cache instances (BagOStuff and WANObjectCache) have their makeKey()