Bug 453206 - [visualizer] update access modifiers to permit extension to
access some fields in MulticoreVisualizer class

Change-Id: Ib5a9141c77825a1f0fd9606d25503c245b397c1c
Reviewed-on: https://git.eclipse.org/r/37019
Reviewed-by: Marc Dumais <marc.dumais@ericsson.com>
Tested-by: Marc Dumais <marc.dumais@ericsson.com>
Cosmetics.