With UI Refresh enabled.

What steps will reproduce the problem?
(1) Open a web page
(2) Open a new tab using the tab grid
(3) Swipe the toolbar to change the tab to the previous one.
(4) Scroll the page

What is the expected result?
Fullscreen should be working.

What happens instead?
Fullscreen is working weirdly, mostly scrolling up hides the toolbar. This is the opposite of the normal behavior.