During the climb the 777 will follow any altitude constraints set in the vertical profile while in VNAV. Between constraints it will climb according to the climb derates and speeds set in the FMC. If there is a cruise constraint set which is below the FMC selected cruise altitude, the FMC will level off at the constraint altitude in VNAV PATH at selected VNAV CLB speed. Fuel and eta predictions will still assume step climbs as weight reduces. If you keep a cruise altitude restraint for the whole cruise segment ( you would not do that, as in practise you would nominate the constraint as a new CRZ ALT) the aircraft levels off in VNAV ALT at ECON CLB SPEED. The FMC calculates the T/D from the constraint altitude. See 777 tech manual 11-30-20(-23)