Full discussion in  crbug.com/786638 

[boliu:]

[For example: test clicks] on a dom object which should start the video playing, but looking at the screenshot, the video never have started. I think this is a general class of flakiness issues with clicking on dom nodes with DOMUtils. Maybe someone can try turning off checks for user gesture, and just click on things with js instead. Probably can't work as a general strategy for all tests, but if this works out well, maybe should consider doing this change more widely.