Malay is probably the right owner.

Just FYI, this is also the case on Linux HiDPI, and it's been driving me nuts ;)
[Chiming in because the OS is marked 'Chrome']

Related bug: https://bugs.chromium.org/p/chromium/issues/detail?id=888263

Looks like it's a hidpi issue (I don't see the problem when I switch to 100% zoom).

This is happening to me on Windows 10.

Is this happening with the new UI as well?

People experiencing this, can you check Dev or Canary?  I know of at least one high DPI bug that would cause this behavior that got fixed a couple weeks ago.

(I was comment #3, but needed to get my @chromium.org account reset.)

Yay, this is mostly fixed in Canary. I found one possibly related bug (on win 10):

1) Set display to 100% zoom.
2) Open Chrome window and an extra tab.
3) Maximize Chrome window.
4) Minimize Chrome window.
5) Set display to 200% zoom.
6) Click Chrome in the taskbar to restore it.

At this point, I think the window is now 1px smaller than the desktop size, but Chrome still shows the top right button as being a maximized window (double squares).  Moving the mouse to the top of a tab shows the vertical resize cursor. Clicking the maximized icon does nothing AFAICT.  If I minimize and restore or move the window, the top right button switches to the maximize button (single square). Once I maximize again, everything is working again.

So I think everything is worked properly except that if the window was in a maximized state and minimized when the zoom is changed, it doesn't update the top right button. If I leave the Chrome window non-minimized when the zoom changes (i.e., omit step 4 above), everything works as expected.

Canary version: 33e646f935a73e694a752ee5cd5ad761efc71809-refs/branch-heads/3564@{#1}

@6: That seems like a legit bug, can you file separately since it sounds like a bugmorph from the original thing here?

Re #4, yes this is happening in the new UI.
Re #5, yes this is fixed (for me anyway) in dev (71.0.3559.6)