[GitHub] jmarantz commented on a change in pull request #1802: Prefer Paint Timing API over chrome.loadTimes()

[GitBox <gi...@apache.org>]

jmarantz commented on a change in pull request #1802: Prefer Paint Timing API over chrome.loadTimes()
URL: https://github.com/apache/incubator-pagespeed-mod/pull/1802#discussion_r224992740
 
 

 ##########
 File path: net/instaweb/rewriter/add_instrumentation.js
 ##########
 @@ -95,6 +95,12 @@ pagespeed.AddInstrumentation.prototype.sendBeacon = function() {
     if (timingApi['msFirstPaint']) {
       // IE.
       firstPaintTime = timingApi['msFirstPaint'];
+    } else if (window['performance']['timeOrigin'] &&
+        window['performance']['getEntriesByName']('first-paint').length > 0) {
+        // Paint Timing API
+        firstPaintTime = Math.floor(
+            window.performance.timeOrigin +
+            window.performance.getEntriesByName('first-paint')[0].startTime);
 
 Review comment:
   I'm a bit OCD when it comes to CSE :)  WDYT of making a temp `winPerf` for window['performance'] and then using it afterward, and likeways for winPerf['getEntriesByName'] and others where you test first and then call, or have chains of dereferencing...
   
   This is just a suggestion, and it would require something like a nested helper function to help you manage the temps in the conditional.

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