From 512fcfdc6082ca6aa60301b6208eb2bc3782ed3b Mon Sep 17 00:00:00 2001
From: Timo Tijhof <krinklemail@gmail.com>
Date: Fri, 20 Apr 2018 01:47:08 +0100
Subject: [PATCH] resourceloader: Remove mwPerformance stub and rename
 mwLoadStart mark

Remove the private 'mwPerformance' stub, in favour of simply calling
performance.mark() directly in a conditional, like we do elsewhere for
web APIs that don't exist in all supported browsers.

This mark (part of the W3C User Timing interface), was sometimes used
to measure a delta to mwLoadEnd, whcih is a problem because startup
loads asynchronously. The point it executes is intentionally variable.
What matters is when the overall JS load process ends, which is composed
of multiple requests.

Keep the mark, but rename to 'mwStartup' which better describes its
purpose and can remain useful.

Bug: T160315
Bug: T192623
Change-Id: I6e2049e7252e5c2be3c5bc6617703b62e5edafb4
---
 maintenance/jsduck/eg-iframe.html    |  3 +--
 resources/src/mediawiki/mediawiki.js |  5 +++--
 resources/src/startup.js             | 10 ++++------
 3 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/maintenance/jsduck/eg-iframe.html b/maintenance/jsduck/eg-iframe.html
index 91e0bc12e3..4c02998d19 100644
--- a/maintenance/jsduck/eg-iframe.html
+++ b/maintenance/jsduck/eg-iframe.html
@@ -35,8 +35,7 @@
 	</script>
 	<script>
 		// Mock startup.js
-		var mwPerformance = { mark: function () {} },
-			mwNow = Date.now;
+		var mwNow = Date.now;
 
 		function startUp() {
 			mw.config = new mw.Map();
diff --git a/resources/src/mediawiki/mediawiki.js b/resources/src/mediawiki/mediawiki.js
index 3fe276bbef..48c1b09fcd 100644
--- a/resources/src/mediawiki/mediawiki.js
+++ b/resources/src/mediawiki/mediawiki.js
@@ -2828,8 +2828,9 @@
 			return $.when.apply( $, all );
 		} );
 		loading.then( function () {
-			/* global mwPerformance */
-			mwPerformance.mark( 'mwLoadEnd' );
+			if ( window.performance && performance.mark ) {
+				performance.mark( 'mwLoadEnd' );
+			}
 			mw.hook( 'resourceloader.loadEnd' ).fire();
 		} );
 	} );
diff --git a/resources/src/startup.js b/resources/src/startup.js
index cc313c7c74..41bcbaad3c 100644
--- a/resources/src/startup.js
+++ b/resources/src/startup.js
@@ -5,11 +5,8 @@
  * - Beware: Do not call mwNow before the isCompatible() check.
  */
 
-/* global mw, mwPerformance, mwNow, isCompatible, $VARS, $CODE */
+/* global mw, mwNow, isCompatible, $VARS, $CODE */
 
-window.mwPerformance = ( window.performance && performance.mark ) ? performance : {
-	mark: function () {}
-};
 // Define now() here to ensure valid comparison with mediaWikiLoadEnd (T153819).
 window.mwNow = ( function () {
 	var perf = window.performance,
@@ -151,8 +148,9 @@ window.isCompatible = function ( str ) {
 	}
 
 	window.mediaWikiLoadStart = mwNow();
-	mwPerformance.mark( 'mwLoadStart' );
-
+	if ( window.performance && performance.mark ) {
+		performance.mark( 'mwStartup' );
+	}
 	script = document.createElement( 'script' );
 	script.src = $VARS.baseModulesUri;
 	script.onload = function () {
-- 
2.20.1