Facing problem to set focus on click of filter/search textbox (ui-grid)

Hi, I am facing problem to set focus on filter/search text box that has been written using ui-grid. Requesting you to see my code in plunker using url

http://plnkr.co/edit/AehpeXTsjAg2ls0muWBs?p=preview

Actually this code is allowing me to filter data as well as navigate data row through keyboard (Up arrow and Down arrow key). Keyboard navigation is working fine but as I click on any of search textbox, dropdown it doesn't keep focus on clicked search textbox/dropdown (you can see by clicking on any of search textbox in above mentioned plunker url).

Please help me to resolve this problem.

Thanks & Regards,

Vishal