Fix selection after inserting nodes

Some surface fragment methods return a clone, so make sure
that is written back to this.fragment in dialogs, as this.fragment.select()
is called on teardown.

Functionally depends on If26cc0a2d in core.

Bug: 65706
Bug: 65716
Change-Id: Ia552b2a4c4c59ffc308a4acdecac78a7803a1c1f