FWIW, this seems to be a recent regression, in the latest dev-channel push.

I think Malay has been doing some changes here.

This seems to be a duplicate of https://bugs.chromium.org/p/chromium/issues/detail?id=766328 which was fixed i M63.
No recent changes have gone into the TopContainerView or tabstrip.

Note that this is not a 100% reliable repro; right now things work correctly on my Teemo, while on my Bob things worked correctly, then when I tried a second time they were broken.

 Issue 766328  was about the tabstrip appearing but having a transparent background - in this case the tabstrip is not appearing at all, nor does the system behave as though it is there but just not visible.

For bisect: My Teemo is running 65.0.3325.9 and does not exhibit the problem, my Bob is on 65.0.3325.35 and does have the problem. I don't know what the previous dev-channel release for Bob was, but I'm pretty sure it didn't have the problem.

Could this be related to the top-pixel above tabs not switching to the tab when clicked?

High-DPI problem?

Otherwise I would look for EventHandlers in ash or in chrome. I don't remember exactly how "reveal" works, but I think it watches all events to detect when the cursor is at the top of the screen.

Neither of the devices I just tested on are running high-DPI, FWIW.

We are behind on beta and if this is intermittent and only in the immersive fullscreen mode it can wait to stable. 

We are still glad to take a fix if we can get one though.

It seems to be permanent once it has started happening; perhaps not
clearing some animation state earlier on, or something?

Re "only in immersive fullscreen", remember that that is the fullscreen
mode directly accessible by a button on the keyboard; having it broken is
surprisingly disruptive, thanks to muscle memory.

I am unable to repro this on Cave 66.0.3343.0 for any of the device scale factor.

I'm no longer able to repro this on ChromeOS 65.0.3325.56 on Bob, FWIW.

Able to reproduce the issue on Chrome 65.0.3325.65/CrOS 10323.30.0- Kevin

Steps :
1. sing in and open the Chrome browser
2. flip the device into tablet mode
3. flip it to exit the tablet mode
4. hit the full-screen button on Keyboard.
5. Move the mouse cursor to the top of the screen.
Then, able to see the issue.

Any update on a fix for this?

This is marked as release block stable for 65, so we need a fix in the next couple weeks.

This happens before any of my changes were submitted to the tab/tabstrip.

#14 
Does the bug persist even after disabling Pixel Canvas? chrome://flags/#enable-pixel-canvas-recording

Can you help confirm if this happens without Pixel Canvas  per comment 21, and pass it back?

Unable to reproduce the issue(#14) on chrome 65.0.3325.148/10323.52.0 - Kevin. Able to see tab-strip & omnibox when moving the mouse cursor to the top of the screen. Works fine with both enable/disabling the Pixel Canvas.