The text in the 777/787 FCTM, mentioned by sleeve wizard:
The rapid descent is normally made with the landing gear up. However, when structural integrity is in doubt and airspeed must be limited, extension of the landing gear may provide a more satisfactory rate of descent.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds.
is identical in the B756 and B737 Flight Crew Training Manuals.