The hidden seek button has custom behavior that causes it to attempt to
"delay" touch events on it, to wait to see
if they are a double-tap or not.
This interacted with the double click to fullscreen behavior
unfortunately; a single touch was registered, then it was
registered again 500ms later, causing it to be detected as a double-tap
by the controls container.
This PR changes the hidden seek button to ignore `touchend` events that
happen while the controls are transparent, and changes the initial
`touchend` event on the hidden seek button to not propagate down, thus
preventing the doubling behavior without introducing any lag on the
controls appearing.
Fixes#9705
Theodore Abshire
a3f4fd40a1