Merge "Inform anonymous A/B test by tracking time from navigationStart"

resources/mediawiki.d.ts

@@ -9,9 +9,16 @@ interface MwUri {
 	toString(): string;
 }
 
+interface MwEventLog {
+	eventInSample( population: Object ): () => boolean;
+	inSample( num: Number ): () => boolean;
+	logEvent( schema: string, data: Object ): () => void;
+}
+
 type UriConstructor = new( uri: string ) => MwUri;
 
 interface MediaWiki {
+	eventLog?: MwEventLog,
 	util: {
 		/**
 		 * @param {string} id of portlet
@@ -80,6 +87,11 @@ interface MediaWiki {
 	 */
 	msg( messageName: string|null ): string;
 
+	/**
+	 * Get current timestamp
+	 */
+	now(): number,
+
 	/**
 	 * Track an analytic event.
 	 *

resources/skins.vector.js/skin.js

@@ -42,6 +42,27 @@ function enableCssAnimations( document ) {
  * @return {void}
  */
 function main( window ) {
+	var now = mw.now();
+	// This is the earliest time we can run JS for users (and bucket anonymous
+	// users for A/B tests).
+	// Where the browser supports it, for a 10% sample of users
+	// we record a value to give us a sense of the expected delay in running A/B tests or
+	// disabling JS features. This will inform us on various things including what to expect
+	// with regards to delay while running A/B tests to anonymous users.
+	// When EventLogging is not available this will reject.
+	// This code can be removed by the end of the Desktop improvements project.
+	// https://www.mediawiki.org/wiki/Desktop_improvements
+	mw.loader.using( 'ext.eventLogging' ).then( function () {
+		if (
+			mw.eventLog &&
+			mw.eventLog.eventInSample( 100 /* 1 in 100 */ ) &&
+			window.performance &&
+			window.performance.timing &&
+			window.performance.timing.navigationStart
+		) {
+			mw.track( 'timing.Vector.ready', now - window.performance.timing.navigationStart ); // milliseconds
+		}
+	} );
 	enableCssAnimations( window.document );
 	collapsibleTabs.init();
 	sidebar.init( window );