Well I don't have 777 documents but for the E190 the figures look something like this:
Speed - 210kt chosen because: a) I have numbers for this speed at all weights. b) Its just behind the drag curve at heavy weights and plenty ahead at light weights (probably the best compromise for fixed speed)
Driftdown not calculated.
Start weight 50T End weight 30T (only the lineage version can carry this amount of fuel)
All Engines operating
FL 300 - 869 minutes
FL 250 - 872 Minutes
FL 150 - 850 minutes
One Engine shutdown
FL 150 - 868 Minutes
These values assume Air conditioning AND Anti-Ice ON. (only tables with fixed speed) So the engine bleed will have them running at higher RPM which probably skews the results a little.
Not sure why I spent an hour on this but there you go.