fdo#77209: Adjust this test to cover clip document use case as well.

Turns out that we do need to share pooled resources with clip documents
in addition to undo documents.

Change-Id: If220c2d4bfc2bece9e884e034525e72dff8e3d66
fdo#77209: Share string pool with clip documents.

We do the same with undo documents, and it will only make sense to do
the same with clip documents as well.  Also, put the sharing part into
a common method (for ease of tracking).

Change-Id: I342b22d95374ee06d16318a66ffea0ac5b42621c