While waiting for this to be addressed properly, you can try the new InfiniteSessionRestore mode, which pauses the inactive tabs initially on start up, then loads them one by one, not all at once, thus not stressing the device. When you switch to a paused tab manually it starts to load immediately. The feature is enabled by enabling the following flags:
chrome://flags/#infinite-session-restore
chrome://flags/#page-almost-idle

FWIW, tentatively suspecting r610309 "Flush microtask queue in DocumentLoader::DetachFromFrame later"
that is I'm assuming the previous beta 71.0.3578.62 was fine and the changelog is:
https://chromium.googlesource.com/chromium/src/+log/71.0.3578.62..71.0.3578.75

Adding Needs-Bisect label for trying a repro and bisect this, cc'ing dcheng@ as well as per C#1. 

Tested the issue on chrome version #71.0.3578.62, reported chrome version #71.0.3578.75 and latest stable #71.0.3578.80 using Windows 7. Below are the observations noted while testing the issue.

Observations:
=============
1.Installed the extension "Ghostery", opened more than 200 tabs. Observed that while clicking Ctrl+t continuously to open new tabs the CPU usage reached 99% and memory to 8.5GB(out of 16GB) in all the three chrome versions.
2.Stopped opening new tabs then CPU usage dropped to 70% and memory to 4GB in all the three versions.

@reporter: Could you please confirm if the issue you are pointing to is while opening tabs or after opening all the tabs, so that it would be really helpful in further triaging of the issue.
Thanks.!

The person with the issue have multiple profiles, each set to "Continue where you left off".
When opening the first such profile, with 150+ tabs, the browser opens, then blocks completely (100% CPU on a quad-core i5) for 30-45 seconds, and afterwards it uses 60+% of the available memory. Opening a second profile makes the entire computer stutter under the load.

The tabs are not just new tabs, they contain actual pages (one profile had a significant number of facebook pages, the other had pages from news-sites).

So, it's both while "opening tabs" (opening and restoring a profile) which blocks everything, and afterwards, where there is significant lag and stuttering for everything else running on the computer.

The user could open three such profiles before (after Chrome 69), now (since Nov 28 beta release) they can only open one, and even that takes heavy work.

(The user is using the old set-up where their primary installation of Chrome is on the beta channel, not a separate installation for beta).

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

haraken@/dcheng@: Could you please have a look into the issue and help further.

Thanks.!