[gtk+] (4 commits) Non-fast-forward update to branch wip/alexl/rendertree

[Alexander Larsson <alexl src gnome org>]

The branch 'wip/alexl/rendertree' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  39c233e... gsk: Add GskRenderTree

Commits added to the branch:

  7bee22b... Avoid some more type checks for internal calls (*)
  8cabfef... GtkCSSImage: Avoid some type checks (*)
  275185d... widget: Avoid typechecks when accessing ->clip and ->alloca (*)
  4fa706b... gsk: Add GskRenderTree

(*) This commit already existed in another branch; no separate mail sent