Version:  50.0.2657.0
OS: ChromeOS

What steps will reproduce the problem?
1. Open a window containing multiple tabs.
2. Drag one of the tabs out to its own window.
3. Click to focus the old window.
4. Click to focus the new window.

What is the expected output? What do you see instead?

Expect that at #2 the new window has a drop-shadow.  Instead it does not.

At #4 the new window does acquire a drop-shadow.

It's possible that this regressed in M49, but I only recently worked out how to repro it.. sorry!