presto-memory-context/src/main/java/io/prestosql/memory/context/MemoryTrackingContext.java/MemoryTrackingContext/newMemoryTrackingContext
class MemoryTrackingContext:    public MemoryTrackingContext newMemoryTrackingContext()
    {
        return new MemoryTrackingContext(
                userAggregateMemoryContext.newAggregatedMemoryContext(),
                revocableAggregateMemoryContext.newAggregatedMemoryContext(),
                systemAggregateMemoryContext.newAggregatedMemoryContext());
    }