WPF DataGrid sample: Add a preview ToolTip to a ScrollViewer

A customer was asking for a sample of a preview ToolTip on scrolling for the DataGrid and Ben Carter, one of our awesome Devs, wrote a sample here for any general ItemsControl.  If you haven’t already, you can download the binaries and source for the DataGrid here. With Ben's sample I've put it to use in the DataGrid.  Pretty much all the work has already been done by Ben's code, I just use the attached behavior he has defined.  I have one DataGrid that has a preview ToolTip similar to his ListBox example and one DataGrid that has a preview ToolTip with the item count.  I've also included a checkbox for changing the scrolling mode from live to defered (more on defered scrolling here).  Check out the DataGrid sample here.