Issue #2642

Example of performance on a MacBookPro laptop:
AddData (BrainAtlas2012.mrb) took 30911 msecs
CloseScene () took 21943 msecs
CloseScene () took 76 msecs
AddData (BrainAtlas2012.mrb) took 29535 msecs
ModifyNode (vtkMRMLScalarVolumeNode1) took 4 msecs
ModifyNode (vtkMRMLScalarVolumeNode2) took 25 msecs
ModifyNode (vtkMRMLScalarVolumeDisplayNode2) took 23 msecs
ModifyNode (vtkMRMLScalarVolumeNode3) took 15 msecs
ModifyNode (vtkMRMLModelHierarchyNode2) took 10 msecs
ModifyNode (vtkMRMLModelNode4) took 0 msecs
ModifyNode (vtkMRMLModelDisplayNode5) took 11 msecs
ModifyNode (vtkMRMLModelHierarchyNode3) took 11 msecs
ModifyNode (vtkMRMLModelStorageNode1) took 5 msecs
AddNode (vtkMRMLModelNode302) took 31 msecs
Layout (3) took 9 msecs
Layout (2) took 27 msecs
Layout (3) took 50 msecs
RestoreSceneView (vtkMRMLSceneViewNode15) took 2701 msecs
RestoreSceneView (vtkMRMLSceneViewNode15) took 1542 msecs

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21583 3bd1e089-480b-0410-8dfb-8563597acbee