Set correct background for subtoolbars - SL #3987
Set correct background for subtoolbars - SL #3987

- remove set_app_paintable from _Box to fix the bad coloring of
  subtoolbars.  The documentation say we can't rely on it to paint the
  themed background when this is set [1].

- don't call Gtk.EventBox.do_draw in the _Box do_draw because that
  will not paint the child toolbar.  Call the child do_draw instead.

- revert 7fc29c9d which was a workaround for the most frequent usage

[1] http://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-set-app-paintable

Signed-off-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>
Acked-by: Simon Schampijer <088e16a1019277b15d58faf0541e11910eb756f6@laptop.org>

tchx84/debian-pkg-sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,godiard/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,godiard/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit