Tested the issue on android and unable to reproduce this issue

Steps to reproduce:
--------------------------
1. Launched chrome and navigated to example.com
2. Scrolled up and down but not seeing any shadow flicker of omnibox as shown in video.

Chrome version:
71.0.3578.12

OS:
Android 9.0 

Android device:
Pixel 2  XL / Pixel 2

@ skyostil: Please check the above steps and let us know if we miss anything. Is this issue consistently reproducible? Please provide device details on which this issue is seen, this would help in further triaging.

Thanks!

It's a little hard to reproduce -- you need to scroll back and forth the spot where the omnibox starts and stops scrolling. Both I and eseckler@ were able to reproduce this consistently.

Also, this was seen on a Pixel 3 XL.

skyostil@ -- Thanks for providing the device details. Could you please confirm whether it is reproduced only on Pixel 3 XL or on any other devices as well. That would help us in verifying & reproducing on the same device.

Assuming that Pixel 3 XL is bezel less device and issue might have reproduced on it. Verifying on other devices will help us in confirming the same.

Couldn't verify on Pixel 3 XL as device is not available with the team.

Thanks!

Yes, it happens on all devices. Just tried on a Nokia 1. Note that it's pretty subtle and non-deterministic so you might have to try a few times to trigger it.

Tested on Pixel 2 XL, Android 9 using Dev #72.0.3591.2 and was not able to reproduce the issue by following the steps provided on various sites. Attached the screencast for reference.

skyostil@ -- Could you please look into the screencast and let us know if anything is missed. Also, request you to update your Chrome Dev to latest #72.0.3591.2 and let us know your observations.

If the issue is still reproduced, please share the build number on which you are observing this issue.

Thanks in advance!

Deleted: 898188.mp4 25.8 MB

898188.mp4 25.8 MB Download

Actually the bug can be seen the video you posted. If you look closely at the shadow below the omnibox, it flickers briefly when the omnibox starts and stops moving.

I was able to reproduce on Pixel 3 XL on Chrome 70.0.3538.04.

ericrk@ could you please take a look?

Bumping priority so we don't miss this.

This repros back to M69 for me, so not a recent regression. My guess is that this is an existing issue that's now more noticeable with the new rounded UI (which has a bigger drop shadow).

Will keep investigating.

over to khushalsagar@ who has some familiarity with the issue.

I think this is related to the whole management of who draws the shadow for the omnibox logic in Android UI. The snapshot for the omnibox also includes this shadow. For the case of static omnibox, where its being rendered by the java UI, we make this shadow invisible to avoid a "double" shadow from both the framework and chrome compositor drawing it. But during animations, when the java omnibox is hidden, the compositor is supposed to draw it. All this is managed using the clip set on toolbar layer here: https://cs.chromium.org/chromium/src/chrome/browser/android/compositor/layer/toolbar_layer.cc?dr=CSs&g=0&l=89

I think this is just the generic issue of framework's updates not being in sync with chrome's rendering causing a momentary flicker. And I'm not sure what the best way to fix this is. +mdjones/dtrainor, any ideas?

Once upon a time I had a patch that made the shadow compositor only (at least in most cases). There was a ton of complexity around showing it when things like omnibox suggestions were visible (any any other android UI for that matter). Now that our design has changed, it might be worth taking another stab at it.

Unfortunately this has always been a problem with the toolbar. I can try the compositor-only approach when I have cycles to spare, but I don't think this is a P1.

I agree, this doesn't need to be a P1. We've had this synchronization issue since the omnibox scroll animation was introduced.

Matt, mind if I assign this to you for following up with the compositor only approach you mentioned?

Yeah that works for me.