Basically I agree with JT
Consider another route, LAX-HKG..about 15 hours in winter. Say the problem occurs 8 hours into the flight.
A cruise descent to 25,000 and continue towards destination at an appropriate econ speed with the luxury of several Japanese airports only 3 or 4 hours ahead. You may even avoid enough of the jetstream to reach HKG with sufficient reserves!
Going the other way, a diversion to ANC or YVR may be required.
IMHO, this does not require an immediate diversion to the nearest suitable airport, nor a descent to 10,000.
(I have been told that apparent loss of all pax OXY was an "indictaion" problem for one airline in the recent past, emergency descent, fuel dumping and diversion ensued....oops!
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