return the selected agent in the Profiling monitor view
called by addViewPage() -handelProfileEvent() - refreshVisiblePage()and
removePage() of the parent class (TraceViewer)
This is for post-filtering needed because of the boundary classes collected even if excluded
by the filter set.
The empty packages are filtered out and
those listed in the active filters for this agent configuration
Three action buttons are defined:
-packageLevel: display all the tree (package/class/method)
-classlevel: display only the class tree
-method level: display only the methods
openSource is takes an object of either a JMessage, JObject or JClass and attempts
to locate the source for the definition of that object within the workbench.