Just to clarify -- this feature has never been available in Chrome per se -- that is, in the headful browser. It would take an effort of a different magnitude to support virtual time in real Chrome given its complexity and security requirements.
The feature was (and still is) available in the headless_shell, which is a different browser (as in "a different content embedder that was only sharing the //content part, not the //chrome part with Chrome"), which was at some point shipped in the same binary as chrome and available as chrome --headless. We're not removing virtual time or manual frame control from headless_shell, we are removing headless_shell from Chrome, which is documented
here.
This article explains the difference between headless_shell and Chrome Headless. You can still use these features by getting headless_shell as described in that article.