WIP: Fixing flaky async tests referenced in #13907

[evmiguel]

This is a work in progress PR. Not ready for review.

Fixes #13907

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[sizebot]

Details of bundled changes.

Comparing: 8ecd4bd...a92d245

scheduler

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
scheduler.development.js	n/a	n/a	0 B	19.17 KB	0 B	5.74 KB	UMD_DEV
scheduler.production.min.js	n/a	n/a	0 B	3.16 KB	0 B	1.53 KB	UMD_PROD

Generated by 🚫 dangerJS

[gaearon]

Thanks for looking into this! We landed a fix in b753f76, but appreciate the initial investigation.

[acdlite]

@evmiguel I'm so sorry that I didn't see this! I had started my branch last night before I went to bed and forgot to check the PRs before I landed it. Otherwise I would have based my work on yours and given you credit. Really appreciate the PR :)