fdo#85886 don't redraw the Navigator content tree if nothing changed

This fixes the flickering of the scrollbar on re-draw once a second.
Perhaps it helps for the performance issue too.

Change-Id: I2ec8f0a8a241b128113bfa3d47fb09ba472b4a7e
ibridges: convert all legacy osl/diagnose.h assertions in source/cppu_uno

Change-Id: I4e78fac76b6bb4923e3b680d910afe5bb9640c33