User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:104.0) Gecko/20100101 Firefox/104.0

Steps to reproduce:

Occasionally experience terrible input lag when using twitch.tv chat. I managed to capture a performance profile which shows the issue.

Actual results:

Chat become unusable due to bad input lag.

Expected results:

Users expect to have zero input lag when typing something.

The Bugbug bot thinks this bug should belong to the 'Core::Layout: Form Controls' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Looks to be lots of time spent in JS

Here is another capture that shows the issue. Notice the DomEvent Keypress duration on marker chart.

In the second profile the problem seems to be magnified by the GC major which is happening concurrently, which requires that we use write barrier.
Making key-presses go from ~300ms to ~520ms.

Then the code seems to spend a lot of time in Proxy related code, as well as js::Call and js::MaybeEnterJit, which suggests that we should optimize the code and start JIT-ing code path for making these calls instead of jumping into C++ to return back in the JIT.

Iain, would you know who might be looking at this issue?