Improved timekeeping logic for USAP Pool refill mechanism.

            if (mUsapPoolRefillTriggerTimestamp == INVALID_TIMESTAMP) {

                pollTimeoutMs = -1;

            } else {

                int elapsedTimeMs =

                        (int) (System.currentTimeMillis() - mUsapPoolRefillTriggerTimestamp);

                long elapsedTimeMs = System.currentTimeMillis() - mUsapPoolRefillTriggerTimestamp;

                if (elapsedTimeMs >= mUsapPoolRefillDelayMs) {

                    // Normalize the poll timeout value when the time between one poll event and the

                    // next pushes us over the delay value.  This prevents poll receiving a 0

                    // timeout value, which would result in it returning immediately.

                    pollTimeoutMs = -1;

                } else if (elapsedTimeMs <= 0) {

                    // This can occur if the clock used by currentTimeMillis is reset, which is

                    // possible because it is not guaranteed to be monotonic.  Because we can't tell

                    // how far back the clock was set the best way to recover is to simply re-start

                    // the respawn delay countdown.

                    pollTimeoutMs = mUsapPoolRefillDelayMs;

                } else {

                    pollTimeoutMs = mUsapPoolRefillDelayMs - elapsedTimeMs;

                    pollTimeoutMs = (int) (mUsapPoolRefillDelayMs - elapsedTimeMs);

                }

            }