Melody, can you help clarify what this is reporting?  I read both feedback reports, and both are very difficult for me to understand.

AFAICT, the second report is maybe saying that the drag handle + resize region of the window frame that appears above the tabs is vertically taller than it used to be.  The first report is maybe saying that the frame became too light-colored and there's insufficient distinction between frame color and tab color.

I'm not certain, though.  Is there any way to reach out to these users for clarification?

Hi Peter,

This topic came up in our feedback review again today and I think we finally figured out what the users are saying.

To reproduce:
1) Drag a tab out of an existing window
2) If it does not default to full screen, you can observe some extra space at the top above the tab
3) If your tab is full screen - take it out of full screen mode. The space above the tabs is vertically taller than it used to be... but only when you're not in full screen.

Here's a new report on this: 
https://listnr.corp.google.com/report/85716102693

***UI Mass Triage ***
Adding labels for expert review.

If this is on Windows, then the space above tabs is shorter than it used to be, rather than taller.  So I'm still confused.