[wasm] spread WS based timers over next 6 minutes to prevent heavy throttling

[pavelsavara]

Problem

Chromium browsers throttle setTimeout frequency on inactive pages to 1 sec almost immediately.
5 minutes later they throttle heavily to wakeup each 60 seconds.
That breaks dotnet Timer expectations and also threadpool.

The heavy throttling could be lifted back to 1sec if there was WebSocket activity.
https://developer.chrome.com/blog/timer-throttling-in-chrome-88/#intensive-throttling

Implementation

The idea is to cover the future 6 minutes with "wakeup" timer, each 1 second apart from each other.
1 second, because is the light throttling rate, so it would not help to try to do it more often.
It should be triggered from WS event, so that it's only 1 deep from it.
Every subsequent call would schedule only for uncovered future.

There is [OuterLoop] unit test for this.

Fixes#51041

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Issue Details

---

Fixes #51041

Author:	pavelsavara
Assignees:	-
Labels:	arch-wasm
Milestone:	-

[pavelsavara]

Right now, I'm not clear if 6 minutes is right time span.
Also I plan to implement OuterLoop unit test for it yet.

[pavelsavara]

This is necessary infrastructure change for the automated test. It's still quite fragile.
dotnet/xharness#695

[pavelsavara]

/azp run runtime-libraries-mono outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

New xharness binaries are in.

[pavelsavara]

/azp run runtime-libraries-mono outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

/azp run runtime-libraries-mono outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

/azp run runtime-libraries-mono outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

/azp run runtime-libraries-mono outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

Outerloop issue is Unable to open X display. for the new System.Net.WebSockets.Client.Wasm.Tests, which makes sense.
But throttling is not testable without real visible browser UI.

[kg]

IIRC there are ways to run chromium headless with a 'fake' framebuffer, window etc. Not sure which one we'd use here, or whether it would actually trigger this. Another option would be a headless X instance paired to VNC, I know people do that for tests sometimes.

[pavelsavara]

I just excluded the test from CI, making it manual test.

[kg]

Everything looks fine to me

[pavelsavara]

/backport to release/6.0-rc1

[github-actions]

Started backporting to release/6.0-rc1: https://github.com/dotnet/runtime/actions/runs/1169555771