[gtk] (10 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  4650f7e... gtk-demo: Cosmetic improvement to listbox2 demo (*)
  2bf9ae0... Adwaita: Small improvement for dropdown (*)
  a85fc00... wayland: Don't send invalid anchor rectangles (*)
  b69dc3d... gtk-demo: Add warnings to the themes demo (*)
  230107c... gtk-demo: Cosmetic improvements to the expander demo (*)
  4290208... gtk-demo: Dark theme support for dnd demo (*)
  2335953... gtk-demo: Cosmetic fixes for the fontrendering demo (*)
  da0955f... gtk-demo: Cosmetic fixes to the textmask demo (*)
  e5247b7... gtk-demo: Finish peg solitaire demo (*)
  66fa530... Merge branch 'matthiasc/for-master' into 'master'

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