Hi Jorge,
Thank you for contacting Syncfusion support.
We were unable to reproduce your issue . We have prepared a sample by using your shared code and placed a Treegrid and Grid with the Datasource and resized the Splitter and thus the Scrollbar appears in the Grid. Could you please share us more details on your requirement on the scroller that is needed in Splitter or in Grid? So that we can help you out better.
Please find the attached sample below.
http://www.syncfusion.com/downloads/support/forum/121196/ze/SplitterGrid1070902594
Please let us know if you have any other queries.
Regards,
Arun P