QtWebkit JS DGrid scrollbar indicator doesn't follow to the cursor position

• Open http://dojofoundation.org/packages/dgrid/tutorials/grids_and_stores/demo/OnDemandGrid.html in the Qt sample browser.
• Move the scrollbar indicator to the bottom
• Keep clicking the middle section of the scrollbar
• Notice the indicator moves up for a while BUT then STOPS, away from the cursor. It should move up until it's under the cursor.

Indicator follows to under the cursor if indicator start point for moving is not bottom of the scrollbar.