1864681 - Cannot gather LargestContentfulPaint on Twitch

Status: NEW

(Testing :: Raptor, defect, P2)

Description

[Greg Mierzwinski [:sparky]]

In bug 1863130, we're adding the LargestContentfulPaint (LCP) metric to the metrics we measure, and alert on, but we're unable to retrieve an LCP value with this Twitch page: https://www.twitch.tv/videos/894226211

It's unclear what's going on. The scripts used to gather it in Browsertime (along with the LargestContentfulPaint API) don't return any results.

Locally, this can be reproduced on Linux by running: ./mach raptor -t twitch --post-startup-delay 1 --page-cycles 1

If you include --debug --verbose it will pause the page so you can debug it further.

Comment 1

[Sean Feng [:sefeng]]

This is a known spec issue such that Twitch uses scrollLeft property and that causes a scroll event which prevent LCP from being generating.

I tested the same site on Chrome and Chrome also doesn't have an LCP entry.

Comment 2

[Greg Mierzwinski [:sparky]]

Ah, good to know, thanks!