message: Change `auto` return type to VectorTreeChildrenList.
diff: @@ -403,6 +403,10 @@ class VectorTree : private _VectorTreeImpl {
  typedef _VectorTreeImpl impl_type;
  public:
  + using VectorTreeChildrenList =
  + vector_tree_internal::VectorTreeChildrenList<std::vector<this_type>>;
  + friend VectorTreeChildrenList;
  +
  // Self-recursive type that represents children in an expanded view.
  typedef std::vector<this_type> subnodes_type;
  typedef T value_type;
  @@ -523,9 +527,9 @@ class VectorTree : private _VectorTreeImpl {
  const this_type* Parent() const { return parent_; }
  - auto& Children() { return children_; }
  + VectorTreeChildrenList& Children() { return children_; }
  - const auto& Children() const { return children_; }
  + const VectorTreeChildrenList& Children() const { return children_; }
  bool is_leaf() const { return children_.empty(); }
  @@ -961,10 +965,6 @@ class VectorTree : private _VectorTreeImpl {
  // operator=(). There should be no need to set it manually in other places.
  this_type* parent_ = nullptr;
  - using VectorTreeChildrenList =
  - vector_tree_internal::VectorTreeChildrenList<std::vector<this_type>>;
  - friend VectorTreeChildrenList;
  -
  // Array of nodes/subtrees.
  VectorTreeChildrenList children_;
  };
  