Merge "Change "slave" => "replica DB" in /includes"

diff --cc includes/MediaWiki.php
index 35aa610,e67a9b5..77a1969
--- 1/includes/MediaWiki.php
--- 2/includes/MediaWiki.php
+++ b/includes/MediaWiki.php
@@@ -580,9 -580,9 +580,9 @@@ class MediaWiki 
                        $request->response()->setCookie( 'UseCDNCache', 'false', $expires, $options );
                }
  
-               // Avoid letting a few seconds of slave lag cause a month of stale data. This logic is
+               // Avoid letting a few seconds of replica DB lag cause a month of stale data. This logic is
                // also intimately related to the value of $wgCdnReboundPurgeDelay.
 -              if ( $factory->laggedSlaveUsed() ) {
 +              if ( $factory->laggedReplicaUsed() ) {
                        $maxAge = $config->get( 'CdnMaxageLagged' );
                        $context->getOutput()->lowerCdnMaxage( $maxAge );
                        $request->response()->header( "X-Database-Lagged: true" );