Don't serialize startTime_
Don't serialize startTime_

It’s intended to measure time since instance created, but:

* There’s no guarantee the resurrected interpreter will use the same
epoch.
* We don’t want to count all the elapsed time between serialisation and
deserialisation.
* In any case the docs for process.hrtime() *specifically* offer not
guarantee about its behaviour when passed a two-element array not
obtained as the return value from a previous call to itself;
roundtripping through JSON might destroy some magic.

NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,google/CodeCity