[gtk] (24 commits) Non-fast-forward update to branch matthiasc/for-master

[Matthias Clasen <matthiasc src gnome org>]

The branch 'matthiasc/for-master' 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:

  56565b1... reftests: Fix the window-show-contents-on-map test
  fa2a8ac... reftests: Remove window-show-contents-on-map from xfails

Commits added to the branch:

  197fe80... testsuite: Fix swapped params in notify test (*)
  18114ba... headerbar: Remove title button separators (*)
  2791c52... headerbar: Remove decoration-layout-set property (*)
  6378905... Move the idle sizer to the gtkroot.c (*)
  f8f391c... gtk-demo: Polish the clipboard demo (*)
  796bc9b... Merge branch 'clipboard-demo-fixes' into 'master' (*)
  f6c8af6... gtk-demo: Improve the dnd demo (*)
  c6fc7d8... gtk-demo: Minor cosmetic fixes (*)
  44e3185... gtk-demo: Remove the colorsel demo (*)
  f645c06... gtk-demo: Update copyright year (*)
  6f7bd37... widget-factory: Update copyright year (*)
  4aa8f6f... Add GtkWindowControls (*)
  5321f8f... headerbar: Use GtkWindowControls (*)
  b5d61eb... docs: Add GtkWindowControls to docs (*)
  7f1e82d... Merge branch 'wip/exalm/titlebuttons' into 'master' (*)
  ccc3874... Merge branch 'clipboard-demo-fixes' into 'master' (*)
  2571a2a... reftests: Fix the window-show-contents-on-map test
  dde32b5... reftests: Remove window-show-contents-on-map from xfails
  ecf8e6f... widget-factory: Improve the layout on page 3
  8410e6f... widget-factory: Some cosmetics
  8de774d... widget-factory: Make print a window action
  1f67c8a... widget-factory: Implement win.print
  0dbe2bc... inspector: Make the resource tab play videos
  fa75035... widget-factory: Put a video widget in

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