Testing that the overflow button is properly marked as `on` only when the context menu is showing.

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".


PASS shadowRoot.querySelector('button.overflow') became different from null
PASS shadowRoot.querySelector('button.overflow').getBoundingClientRect().width became different from 0
Tapping overflow button...
PASS shadowRoot.querySelector('button.overflow').classList.contains('on') became true
Dismissing contextmenu...
PASS shadowRoot.querySelector('button.overflow').classList.contains('on') became false
PASS successfullyParsed is true

TEST COMPLETE