Chrome Version: 70.0.3538.110 (perhaps the problem appeared with the introducing PiP support).
OS Version: Android 8+, device with hardware navigation buttons.

What steps will reproduce the problem?
1. go to page, containing video and start video playing
2. switch video to full screen mode
3. immediately minimize the browser (go to home screen by pressing hardware "Home" button)

Expected result: browser goes to PiP mode and small floating window appears on the screen


Actual result: browser just goes to background and no PiP window is displaying.

Note: if wait a moment after step #2 - the PiP will be displayed normally.


This is due to delays determining full-screen mode in the class `MediaCustomControlsFullscreenDetector`. When receiving full-screen events (for example, `EventTypeNames::webkitfullscreenchange`), the detector waits one second before checking whether we have switched to full-screen mode (see `check_viewport_intersection_timer_` and `OnCheckViewportIntersectionTimerFired method`). 
The timer was added to make sure that when we do the checks all the layout changes are in place and we don't end up with some race conditions that would make the feature never work on the page.

We need to somehow get rid of this delay: either reduce it or thing about other solutions.

Check the details in this discussion: https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/FRJeEZVUR_0