Since the verical filmstrip doesn't set its width explicitly anymore,
calculating the available area for the large video based on the
filmstrip width retrieved from the HTML element was wrong
in the cases when the rendering and cleanup of the filmstrip hasn't
finish yet. For example when switching from tile view to stage view.
Filmstrip remote thumbnails display under certain conditions, as
defined in filmstrip/functions.web.js. Previously the raw
participant count was used, which included fake participants.
Using the selector getParticipantCount excludes fake participants,
causing YouTube thumbnails to remain hidden in a 1-on-1 call.
Hristo Terezov
Leonard Kim
Bettenbuk Zoltan