Apple (r52507) and than the Gtk port (r52605) disabled datagrid implementation as it is not ready for general web use yet. In general trunk is meant for development and features under development are expected to be turned on, so I'm not sure if Qt port should follow other ports as well on the trunk to turn this feature off by default.
However I would propose to turn off datagrid support on the 4.6 productization branch. Patch is attached, but not put up for review as at this point this is not for trunk.
Created attachment 45637 [details]
Yeah, we should turn it off, the layout tests are also disabled.
Committed r52648: <http://trac.webkit.org/changeset/52648>
Cherry-picked into qtwebkit-4.6 as commit da94856dacd1a6a5a788def840255a6fdc1f85b7