Can you please attach a screencast of the issue? Thanks in advance.

Yep, screencast is important here, especially showing the mouse pointer.

Unable to reproduce the issue on reported chrome version 69.0.3497.81 using Windows 10 with the below mentioned steps.
1. Launched Chrome
2. Opened around 30 new tabs.
3. Closed 15-20 tabs.
Observed the tabs going back to the normal size, when each tab is being closed.

@Reporter: Could you please provide a screencast of the issue as asked in comment#1 and comment#2, which helps us to triage it further in a better way. Any additional inputs from your end in reproducing this would be more helpful.

Thanks!

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

@6: Your mouse cursor is still within the tabstrip-shouldn't-resize area.  What happens if you move it down to the middle of the webpage?

It resizes after about 3-5 seconds after I move the curser. Could not get a fast enough screenshot when I moved the curser. I am not bothered by this, just wanted to inform you.

It should be about one second after you move the mouse cursor out.

As long as that's happening, there's no bug -- not resizing tabs while the mouse is still over them is intentional, so you can keep closing tabs with the mouse and having another close button move under your mouse pointer.  This behavior has been in Chrome since the initial public launch.