wayland/egl: Ensure EGL surface is resized on DRI update_buffers()
Fullscreening and unfullscreening a totem window while playing a video sometimes results in the video subsurface not changing size along. This is also reproducible with epiphany.
If a surface gets resized while we have an active back buffer for it, the resized dimensions won't get neither immediately applied on the resize callback, nor correctly synchronized on update_buffers(), as the (now stale) surface size and currently attached buffer size still do match.
There's actually 2 things to synchronize here, first the surface query size might not be updated yet to the wl_egl_window's (i.e. resize_callback happened while there is a back buffer), and second the wayland buffers would need dropping if new surface size differs with the currently attached buffer. These are done in separate steps now.
v2: Added the 'Fixes' tag