[gtk+] (18 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:

  daf0ddb... gsk: Add GskRenderTree
  a461d84... Use the .symbolic.png assets in Adwaita
  812c73f... Refactor some css transition code slightly
  8b23fa9... Use _gtk_widget_get_window more
  5ae6e92... Use gtk_internal_return_val_if_fail here
  72f6f12... Use an internal parameter check here as well
  d57f5de... Remove an unnecessary check

Commits added to the branch:

  b46da27... gdk/wayland: Add support for the gtk-enable-primary-paste g (*)
  ae61220... gdk/wayland: Handle non-existant gsettings keys (*)
  4f0cf47... Use the .symbolic.png assets in Adwaita (*)
  d9bc675... Refactor some css transition code slightly (*)
  a013a16... Use _gtk_widget_get_window more (*)
  ecd0ce3... Use gtk_internal_return_val_if_fail here (*)
  c1dc36d... Use an internal parameter check here as well (*)
  9133ec5... Remove an unnecessary check (*)
  4c7ddbf... cssimage: Fix cross-fade (*)
  8a83362... Document -gtk-icon-filter (*)
  249a0b1... Some updates to the migration guide (*)
  882290b... Skip dynamic type check in css value getters (*)
  2f453cc... gsk_rounded_rect_init_copy: Don't normalize (*)
  65ad254... Snapshot: Only record names if inspector is recording (*)
  f67ae85... GtkSnapshot: Move collect data to a union in the state (*)
  6341fab... GtkSnapshot: Reuse snapshot state objects (*)
  68a27a9... gtkcssgadget: Use private non-checking versions of gtk_widg (*)
  39c233e... gsk: Add GskRenderTree

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