[425507]use GapContentPosition to track position in layout boxes

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=425507
Change-Id: I371513ba433c4a6cc90ee79b94038078eb7ee0b0
Signed-off-by: Carsten Hiesserich <carsten.hie@gmail.com>
4 files changed