+* ResourceLoader now loads all scripts asynchronously. The top-queue and
+ startup modules are no longer synchronously loaded.
+* 'mediawiki.ui.button' styles are no longer unconditionally loaded on every
+ page. During the deprecation period, the styles will only be loaded on pages
+ which contain 'mw-ui-button' in their HTML. Starting in 1.28, the styles will
+ only be loaded if explicitly required.