[gtk] (2 commits) Non-fast-forward update to branch wip/dboles/overlay-docs-3

[Daniel Boles <dboles src gnome org>]

The branch 'wip/dboles/overlay-docs-3' 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:

  e1d1ee4... Overlay: Use documented parameter name @ reorder()

Commits added to the branch:

  edd28a5... Overlay: Use @index_, not @position, in reorder()
  50a43b1... Overlay: Document overlay children aren't measured