/**
* Creates a new app handle. The handle will wait for an incoming connection for a configurable
* amount of time, and if one doesn't arrive, it will transition to an error state.
*/
ChildProcAppHandle newAppHandle(String secret) {
ChildProcAppHandle handle = new ChildProcAppHandle(secret, this);
ChildProcAppHandle existing = pending.putIfAbsent(secret, handle);
CommandBuilderUtils.checkState(existing == null, "Multiple handles with the same secret.");
return handle;
}