In the 11.2 SR7 this issue was fixed.
56549 Plugin - Container object with chart - Scroll Bar is missing from the chart
55009 (WebView/Ajax) Scrolling with mouse wheel not working when the orientation of a chart was changed from horizontal to vertical
55711 Enable X-Axis Scrollbar setting cause problems when changing to a pie chart
59039 WebView/AJAX: horizontal scroll bar not displayed but shown by only dragging to extend the box
The AJAX client will ignore all scroll bar settings except widths. The AJAX client does not allow users to change scroll bar settings.