Prepare ULS for EventLogging

This change introduces a new configuration variable, $wgULSEventLogging. When
set to true, ULS will register an EventLogging schema module for
<http://meta.wikimedia.org/wiki/Schema:UniversalLanguageSelector>,
making it possible to log events using `mw.uls.logEvent`. When false, the
schema module is not loaded, and `mw.uls.logEvent` is a no-op.

Change-Id: I7139e67cc2f830a6b4b3c8ff1fc72dfcdec9a699

resources/js/ext.uls.init.js

@@ -116,6 +116,33 @@
 		return !/MSIE [67]/i.test( navigator.userAgent );
 	};
 
+	/**
+	 * Local wrapper for 'mw.eventLog.logEvent' which handles default params
+	 * and ensures the correct schema is loaded.
+	 *
+	 * @param {Object} data Event action and optional fields
+	 * @since 2013.07
+	 * @see https://meta.wikimedia.org/wiki/Schema:UniversalLanguageSelector
+	 */
+	mw.uls.logEvent = $.noop;
+
+	// If EventLogging integration is enabled, set event defaults and make the
+	// the function call event logging with correct schema.
+	if ( mw.config.get( 'wgULSEventLogging' ) ) {
+		mw.loader.using( 'schema.UniversalLanguageSelector', function () {
+			mw.eventLog.setDefaults( 'UniversalLanguageSelector', {
+				version: 1,
+				token: mw.user.id(),
+				contentLanguage: mw.config.get( 'wgContentLanguage' ),
+				interfaceLanguage: currentLang
+			} );
+
+			mw.uls.logEvent = function ( event ) {
+				mw.eventLog.logEvent( 'UniversalLanguageSelector', event );
+			};
+		} );
+	}
+
 	/**
 	 * i18n initialization
 	 */