Chrome Version: 73.0.3643.0 (Official Build) dev (32-bit)
OS: Android 9; Pixel 2 Build/PQ1A.190105.004

What steps will reproduce the problem?
(1) Install Twitter Lite PWA on top of Chrome Dev Channel
(2) Sign in, browse timeline
(3) Fling-scroll down somewhat rapidly. Avatar icon and "Home" description disappear. 
(4) Touch screen to stop the scroll.
(5) Wait.

What is the expected result?

Expect to see only Twitter's four icons (home, search, notifications, messages) at the top of the screen.


What happens instead?

After a second or so, the avatar and "home" header reappear.

This seems to be caused by some small (1-pixel?) scroll event being sent by the browser to the page. It only seems to happen in the PWA; I haven't seen it from visiting mobile.twitter.com in Chrome Dev manually.

These are the most reliable reproduction steps I've found. It also sometimes happens when viewing an image or thread, and then going back to the timeline view.

I'm sorry for not reporting this bug earlier; it first showed up probably a few weeks ago. Finally figured out a reliable reproduction.

Could people who work on scrolling please triage this and try to think if recent changes to fling scrolling behavior might have regressed this? Thanks.

This behavior could cause a lot of user frustration on many mobile web pages and PWAs. Marking P1, Regression, R-B-S for M73.