1893287 - The dynamic toolbar moves the page when the fingers are lifted at the end of a scroll (with toolbar-on-top)

Status: NEW

(GeckoView :: Core, defect)

Description

[Markus Stange [:mstange]]

Attachment: screen recording

Steps to reproduce:

1. In Firefox for Android, enable the dynamic toolbar and put it at the top.
2. On a simple page like https://www.mozilla.org/en-US/ , scroll until the dynamic toolbar is half-shown.
3. Lift your finger.

Expected results:
The page should stay in the position where you left it.
The toolbar should animate in or out without moving the page.
If the toolbar wants to hide, but the page is so close to the top that hiding the toolbar would leave negative space at the top, then the toolbar should not hide and instead appear fully, and do so without moving the page.

Actual results:
As the toolbar animates, it moves the page along with it.

This is really jarring. When I read a web page, I position the text I'm reading where I want to read it. I do not pay attention to the position of the dynamic toolbar. When I lift my fingers, I want the text to stay where I put it.
When the browser moves the page out from under me, it ignores my choice of where I positioned the page on the screen.