VTK-2668 - reintroduce using Web Worker if supported (earlier tests that failed seem to work now)
VTK-2668 - reintroduce using Web Worker if supported (earlier tests that failed seem to work now)

vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk