enable-throttle-display-none-and-visibility-hidden-cross-origin-iframes flag

[corelema]

Hello!

I have been looking into a performance issue where an iframe hidden by "display: none" would be throttled.

I found that the flag "enable-throttle-display-none-and-visibility-hidden-cross-origin-iframes" could be responsible for this throttling, however I don't see it at all in edge://flags (while I can find it in chrome). Has it been fully enabled/disabled?
Is there anything else than this flag that could explain the throttling I am seeing? Testing in chrome with or without the flag doesn't make any difference (but removing "display: none" makes a huge difference).

Thanks!

[captainbrosset]

Interesting, the flag isn't in Edge indeed. Even if Edge is also based on Chromium, it's not surprising that there would be subtle differences like this one. That being said if you tested in chrome with/without the flag and it didn't make a difference, then it's most likely something else.

Curious: how do you test for performance in the hidden iframe? What tool do you use?

[corelema]

@captainbrosset I did some performance profiling with the DevTools. It accentuates the slowness with the added overhead, so that's pretty easy to replicate by doing some "heavy" task in an iframe while "display: none" is applied to it. In our case we're loading/parsing/executing JS in it.

I know it's probably something else than this flag, but I'm still curious as to what Edge is/isn't doing in this case (there must be something I would imagine)