ETOPS,
Actually, NoD is on the right line. The 777 does have the ability to move the flaps to maintain speed on final approach, but it is neither mentioned on the technical course, or in the Technical Manual.
With F30 set for landing, if the speed starts to reduce significantly below the bugged speed, then the TE flaps do infact retract slightly to reduce the drag, and hence recover the lost speed, without excessive (if any) thrust lever movement. Conversely, if the speed gets too high, then the TE flaps will extend slightly from the nominal F30 position to increase the drag and bring the speed back again.
The whole idea being to maintain a (relatively) constant thrust setting on final approach.
However, I doubt either would be of sufficient magnitude as to be seen by someone watching the aircraft landing.
Hope this helps.