Fixed display of wrong context menu

Fixed display of wrong context menu

[Title] Fixed display of wrong context menu on scrolling
[Issue#] WEB-3122
[Problem] After scrolling in a page the selection goes
   behind a element and the context menu changes
[Cause] When selection appears to be behind as there is
   a element which is having higher z-index. Once point for
   display of context menu is sent, the hittest function in
   context menu will not the selection range as the display
   point overlaps the element having higher zindex and the
   context menu will differ
[Solution] Will not display the context menu and handles
   if there is element of higer zindex present on top of
   selected text

Change-Id: Ica1e4d7d70068bcafe38851bf191bc7d4035cd20