Load icons on-demand
Load icons on-demand

Because loading icons takes a noticable performance, this code loads the
pixbuf on demand and only loads icons for rows that are visible. There
is a few caveats to this:
- The pixbuf cell renderer must report the proer size even if the icon
  is not yet loaded. This is achieved by setting a fixed size.
- On theme changes the cahced pixbufs and the cell renderer must be
  updated to conform to the new theme.

Distrotech/gtk2,ebassi/gtk,jessevdk/gtk,bratsche/gtk-,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,Adamovskiy/gtk,Lyude/gtk-,bratsche/gtk-,bratsche/gtk-,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,Adamovskiy/gtk,jigpu/gtk,ebassi/gtk,nacho/gtk-,Sidnioulz/SandboxGtk,ahodesuka/gtk,ahodesuka/gtk,ahodesuka/gtk,chipx86/gtk,chipx86/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,alexlarsson/gtk,davidt/gtk,chipx86/gtk,jigpu/gtk,Lyude/gtk-,davidt/gtk,grubersjoe/adwaita,ebassi/gtk,msteinert/gtk,ahodesuka/gtk,jadahl/gtk,msteinert/gtk,jigpu/gtk,Unity-Technologies/gtk,alexlarsson/gtk,simokivimaki/gtk,chergert/gtk,bratsche/gtk-,davidgumberg/gtk,jigpu/gtk,ahodesuka/gtk,Distrotech/gtk2,alexlarsson/gtk,nacho/gtk-,chergert/gtk,simokivimaki/gtk,bratsche/gtk-,chergert/gtk,johne53/MB3Gtk-2,bratsche/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,Distrotech/gtk,Lyude/gtk-,grubersjoe/adwaita,davidt/gtk,johne53/MB3Gtk-2,alexlarsson/gtk,chipx86/gtk,Lyude/gtk-,simokivimaki/gtk,jadahl/gtk,davidgumberg/gtk,ebassi/gtk,Adamovskiy/gtk,Unity-Technologies/gtk,davidgumberg/gtk,msteinert/gtk,msteinert/gtk,ahodesuka/gtk,chergert/gtk,Unity-Technologies/gtk,chergert/gtk,nacho/gtk-,Lyude/gtk-,jigpu/gtk,jigpu/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,johne53/MB3Gtk-2,msteinert/gtk,grubersjoe/adwaita,davidgumberg/gtk,davidt/gtk,grubersjoe/adwaita,Sidnioulz/SandboxGtk,ahodesuka/gtk,nacho/gtk-,alexlarsson/gtk,alexlarsson/gtk,Distrotech/gtk2,Distrotech/gtk,Lyude/gtk-,Lyude/gtk-,Sidnioulz/SandboxGtk,Adamovskiy/gtk,davidt/gtk,grubersjoe/adwaita,Distrotech/gtk,jessevdk/gtk,johne53/MB3Gtk-2,Lyude/gtk-,chipx86/gtk,alexlarsson/gtk,jadahl/gtk,ebassi/gtk,Sidnioulz/SandboxGtk,chergert/gtk,davidt/gtk,davidgumberg/gtk,jigpu/gtk,jadahl/gtk,Distrotech/gtk2,simokivimaki/gtk,simokivimaki/gtk,Adamovskiy/gtk,ebassi/gtk,alexlarsson/gtk,jadahl/gtk,Unity-Technologies/gtk,Distrotech/gtk,grubersjoe/adwaita,johne53/MB3Gtk-2,jadahl/gtk,jessevdk/gtk,jessevdk/gtk,davidgumberg/gtk,davidgumberg/gtk,Distrotech/gtk2,Unity-Technologies/gtk,jessevdk/gtk,msteinert/gtk,Distrotech/gtk,chergert/gtk,simokivimaki/gtk,jessevdk/gtk,Distrotech/gtk2,nacho/gtk-,jessevdk/gtk,ahodesuka/gtk