MediaWiki 1.26, in where ResourceLoader became fully asynchronous.
* $wgMasterWaitTimeout was removed (deprecated in 1.24).
* Fields in ParserOptions are now private. Use the accessors instead.
+* Custom LESS functions (defined via $wgResourceLoaderLESSFunctions)
+ have been removed, after being deprecated in 1.24.
=== New features in 1.26 ===
* (T51506) Now action=info gives estimates of actual watchers for a page.