[gtk] (8 commits) Non-fast-forward update to branch wip/exalm/headerbar-dragging

[Alexander Mikhaylenko <alexm src gnome org>]

The branch 'wip/exalm/headerbar-dragging' 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:

  3e858d5... widget: Pass parent to gtk_widget_consumes_motion()
  8881712... window: Make gtk_window_update_toplevel() non-static
  864cc86... Add GtkWindowHandle
  430bf34... headerbar: Use GtkCenterBox internally
  bf8bb6e... headerbar: Include GtkWindowHandle
  ddd3df9... window: Stop handling dragging and titlebar actions

Commits added to the branch:

  81c68b8... inspector: Fix css tree popovers (*)
  8bb1330... Merge branch 'fix-inspector-popover' into 'master' (*)
  8978ef6... widget: Pass parent to gtk_widget_consumes_motion()
  494848d... window: Make gtk_window_update_toplevel() non-static
  3431a9c... Add GtkWindowHandle
  f4c38ba... headerbar: Use GtkCenterBox internally
  b9b5f2b... headerbar: Include GtkWindowHandle
  643e3c3... window: Stop handling dragging and titlebar actions

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