Previously the EGL backend was directly prodding the width/height
members of the framebuffer structure when a configure notify event is
received. However this doesn't set the dirty flag for the viewport so
Cogl will continue using the wrong viewport y offset. The GLX backend
is already using an abstraction for updating the size which does set
the flag. This patch just makes the EGL backend also use that
abstraction.
1d67085e8a