Prefixing everything with a constant packagename is not needed for
internal keys, and just adds complexity.
Rename ARGUMENT_ prefix to ARG_ to match (most) of the rest of the
codebase.
Restrict visiblity of above as much as possible.
FRAGMENT_ID wasn't actually the fragment's ID (that's misleading, and
sounds like the tag). It's actually the layout resource ID. There's no point in making that a static constant.
Mike Harris