Add a scrolling test case involving creating new rows in tree stores
Add a scrolling test case involving creating new rows in tree stores

Based on a bug report from Miroslav Rajcic, details are in the tree view
scrolling suite source code.

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