clutter: Wait to know the video size before computing it's final size
clutter: Wait to know the video size before computing it's final size

Instead of hardcoding its size to 400x300 and thus its aspect ratio to
4/3.

nzjrs/pinpoint,michaelgwood/pinpoint,tyll/pinpoint,danigm/pinpoint,nekohayo/pinpoint,robclark/pinpoint,GNOME/pinpoint,nekohayo/pinpoint,danigm/pinpoint,GNOME/pinpoint,bpeel/pinpoint,michaelgwood/pinpoint,robclark/pinpoint,tyll/pinpoint,bpeel/pinpoint,nzjrs/pinpoint,robclark/pinpoint,potofcoffee/pinpoint,potofcoffee/pinpoint