iconview: layout items immediately when setting a GtkTreeModel
iconview: layout items immediately when setting a GtkTreeModel

As the draw handler expects the items to be laid out already, we cannot
queue a layout here to avoid a race condition with the resize that is
queued immediately after, which in turn would lead to a segfault later
in the paint_item() implementation.

https://bugzilla.gnome.org/show_bug.cgi?id=663138

davidt/gtk,msteinert/gtk,bratsche/gtk-,Distrotech/gtk2,bratsche/gtk-,Sidnioulz/SandboxGtk,grubersjoe/adwaita,msteinert/gtk,jessevdk/gtk,chergert/gtk,chergert/gtk,Sidnioulz/SandboxGtk,alexlarsson/gtk,ebassi/gtk,jadahl/gtk,jigpu/gtk,ahodesuka/gtk,alexlarsson/gtk,Adamovskiy/gtk,chergert/gtk,msteinert/gtk,ebassi/gtk,jadahl/gtk,davidt/gtk,ahodesuka/gtk,ahodesuka/gtk,alexlarsson/gtk,Lyude/gtk-,chergert/gtk,bratsche/gtk-,Distrotech/gtk2,davidt/gtk,jadahl/gtk,jadahl/gtk,jadahl/gtk,jessevdk/gtk,jigpu/gtk,Lyude/gtk-,jadahl/gtk,ahodesuka/gtk,ebassi/gtk,davidgumberg/gtk,Lyude/gtk-,bratsche/gtk-,Lyude/gtk-,jessevdk/gtk,msteinert/gtk,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,Sidnioulz/SandboxGtk,ebassi/gtk,jigpu/gtk,Lyude/gtk-,Adamovskiy/gtk,alexlarsson/gtk,chergert/gtk,bratsche/gtk-,Lyude/gtk-,ahodesuka/gtk,Lyude/gtk-,msteinert/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,Distrotech/gtk2,ahodesuka/gtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,ebassi/gtk,grubersjoe/adwaita,jessevdk/gtk,Adamovskiy/gtk,ahodesuka/gtk,davidgumberg/gtk,Adamovskiy/gtk,Lyude/gtk-,davidgumberg/gtk,jadahl/gtk,alexlarsson/gtk,davidt/gtk,ebassi/gtk,Distrotech/gtk2,jessevdk/gtk,Adamovskiy/gtk,grubersjoe/adwaita,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,Distrotech/gtk2,jigpu/gtk,chergert/gtk,Adamovskiy/gtk,davidt/gtk,jessevdk/gtk,jigpu/gtk,bratsche/gtk-,grubersjoe/adwaita,davidgumberg/gtk,alexlarsson/gtk,davidt/gtk,msteinert/gtk,davidgumberg/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,jigpu/gtk,jessevdk/gtk,alexlarsson/gtk,ahodesuka/gtk,chergert/gtk,Distrotech/gtk2,chergert/gtk