ClutterGroup previously calculated the size as the distance from the
left edge of the leftmost child to the right edge of the rightmost
child except if there were any chidren left of the origin then the
left edge would be zero.
However the group is always allocated its size relative to its
origin so if all of the children are to the right of the origin then
the preferred size would not be large enough to reach the rightmost
child.
origin
┼──────────┐
│Group │
│ ┌────────┼─┐
│ │Child │ │
│ │ │ │
└─┼────────┘ │
│ │
└──────────┘
group size
╟──────────╢
This patch makes it so the size is always just the rightmost edge.
origin
┼────────────┐
│Group │
│ ┌──────────┤
│ │Child │
│ │ │
│ │ │
│ │ │
└─┴──────────┘
group size
╟────────────╢
Fixes bug:
http://bugzilla.openedhand.com/show_bug.cgi?id=1825
