message: Fix a memory corruption issue in boosted trees as the iterators become invalid after an Add.
diff: @@ -126,7 +126,8 @@ class DecisionTreeEnsembleResource : public StampedResource {
  return;
  }
  used_ids->Add(handler_id);
  - std::rotate(first, used_ids->end() - 1, used_ids->end());
  + // Keep the list of used handlers sorted.
  + std::sort(used_ids->begin(), used_ids->end());
  }
  std::vector<int64> GetUsedHandlers() const {
  