The metrics for throughput probing include timesIncreased, timesDecreased, totalAmountIncreased, totalAmountDecreased, and resizeDurationMicros. However, timesDecreased and totalAmountDecreased are never updated, since the _probeDown method mistakenly increments timesIncreased and totalAmountIncreased.

This is making it harder to diagnose problems with throughput probing. We should fix this and backport it to affected versions.