McLaren added these floor details (yellow) as part of the Barcelona update
McLaren ran a variety of new details on the MP4-25 in Barcelona, which included this new duct in the floor. Sitting just ahead of the tyre, this lets air pass from above to below the floor, which then passes the coved section of florr beside the diffuser. The coved (ridged) section was first used on the RB5 and has been copied by several teams. However so far no one has gone as far as McLaren in makign the top deck of the diffuser reach up as far the full width of the beam wing. McLaren have even added a slot to this section to keep the flow attached.
McLaren ran this vent with both a rear facing outlet and louvers
Additionally the team ran with different cooling outlets by the cockpit, some of these featured both an rear facing outlet and louvers along its top and side surfaces.
Scarbsf1's Blog 