This could be related to some of saman's recent work. Adding myself to cc too. Saman, thoughts?

When this happens, the keyboard shortcuts also stop working (e.g. ctrl+w does not close the tab anymore).

I used the ui-devtools a little bit to see if anything interesting shows up. I noticed that the NativeViewHostAuraClip window is somehow stacked underneath the Widget's window. That could be the issue too. Did any changes happen recently that would affect the window-stacking in aura.

Ohh, if keyboard shortcuts stop working then I don't think this is Viz related?

Can you elaborate the repro step? How did you create a window with existing tab?

Close a window with tabs, ctrl-shift-t, for example.

I couldn't repro this on ToT (72.0.3623.0/11264.0.0). Is this still happening?

It is still happening for me, yes.

Google Chrome	72.0.3609.3 (Official Build) dev (64-bit)
Revision	7e51571a56ab79bbd1683dc2245b031e32126ec3-refs/branch-heads/3609@{#4}
Platform	11264.0.0 (Official Build) dev-channel cave
Firmware Version	Google_Cave.7820.384.0
Customization ID	ASUS-CAVE
ARC	5132105

Hm interesting. I can repro only on my corp profile, but not with my @chromium.org profile, on the same device. Perhaps this is related to some extension I have on my corp profile, or some flag I have turned on for my corp profile. I will investigate more when I switch back to the corp profile.

+fdoray@ in case he has an idea.

It looks like the 'Show taps' flag (for showing the active touch-points on screen) is the culprit here. Perhaps the flag creates a large fullscreen transparent window, and it confuses the occlusion-tracker to mark the windows as occluded?

You are definitely right that 'show tabs' results in a fullscreen transparent window. Xiyuan, could you take a look at this as it is likely related to occlusion tracking with the window service.

When wiring occlusion tracking for Window Service, I made an assumption that a remote window is always opaque. TapVisualizer is a remote window but it is transparent, which breaks the assumption.

Any insights of what could a better signal to detect such remote transparent window?

I think you should key off the transparency of the aura::Window that is created. We may need to better update that, but I would start there.

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The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bdffcf67c196f1799e5aff5f7ced62a02bd87353

commit bdffcf67c196f1799e5aff5f7ced62a02bd87353
Author: Xiyuan Xia <xiyuan@chromium.org>
Date: Fri Nov 30 20:51:25 2018

Fix remote window occlusion tracking

- Add a kClientWindowHasContent property to pass the info
  from client to Window Service;
- DesktopWindowTreeHostMus sets the property based on layer type
  and opacity of Widget::InitParams;
- Check kClientWindowHasContent property as part of the remote
  window has-content check for occlusion tracking;

Bug:  908629 
Change-Id: I23c582d7135d50b70ba0776cb0368da59fe5d8c7
Reviewed-on: https://chromium-review.googlesource.com/c/1354439
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612773}
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/services/ws/public/mojom/window_manager.mojom
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/services/ws/window_service.cc
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/services/ws/window_tree_unittest.cc
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/ui/aura/client/aura_constants.cc
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/ui/aura/client/aura_constants.h
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/ui/aura/mus/property_converter.cc
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/ui/views/mus/desktop_window_tree_host_mus.cc
[modify] https://crrev.com/bdffcf67c196f1799e5aff5f7ced62a02bd87353/ui/views/mus/desktop_window_tree_host_mus_unittest.cc

Your change meets the bar and is auto-approved for M72. Please go ahead and merge the CL to branch 3626 manually. Please contact milestone owner if you have questions.
Owners: govind@(Android), kariahda@(iOS), djmm@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782

commit b3ad63e7515b8efe06b618c3b5d1c1775c0dd782
Author: Xiyuan Xia <xiyuan@chromium.org>
Date: Tue Dec 04 16:31:04 2018

Merge M72 "Fix remote window occlusion tracking"

> - Add a kClientWindowHasContent property to pass the info
>   from client to Window Service;
> - DesktopWindowTreeHostMus sets the property based on layer type
>   and opacity of Widget::InitParams;
> - Check kClientWindowHasContent property as part of the remote
>   window has-content check for occlusion tracking;
> 
> Bug:  908629 
> Change-Id: I23c582d7135d50b70ba0776cb0368da59fe5d8c7
> Reviewed-on: https://chromium-review.googlesource.com/c/1354439
> Reviewed-by: Tom Sepez <tsepez@chromium.org>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#612773}
> (cherry picked from commit bdffcf67c196f1799e5aff5f7ced62a02bd87353)

Change-Id: I816aa5a7c7d69c060387dd4ed86f639ab0a591f7
Reviewed-on: https://chromium-review.googlesource.com/c/1361302
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/branch-heads/3626@{#28}
Cr-Branched-From: d897fb137fbaaa9355c0c93124cc048824eb1e65-refs/heads/master@{#612437}
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/services/ws/public/mojom/window_manager.mojom
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/services/ws/window_service.cc
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/services/ws/window_tree_unittest.cc
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/ui/aura/client/aura_constants.cc
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/ui/aura/client/aura_constants.h
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/ui/aura/mus/property_converter.cc
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/ui/views/mus/desktop_window_tree_host_mus.cc
[modify] https://crrev.com/b3ad63e7515b8efe06b618c3b5d1c1775c0dd782/ui/views/mus/desktop_window_tree_host_mus_unittest.cc