Position info (item n of m) incorrect if hidden focusable items in list

Bug: 836997
Change-Id: I971fa7076f72d51829b36af8e379260d48ca25ec
Reviewed-on: https://chromium-review.googlesource.com/c/1450235
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628890}
int32_t AXTree::GetPosInSet(const AXNode& node, const AXNode* ordered_set) {
  if (ordered_set_info_map_.find(node.id()) == ordered_set_info_map_.end())
    ComputeSetSizePosInSetAndCache(node, ordered_set);
  return ordered_set_info_map_[node.id()].pos_in_set;
}

int32_t AXTree::GetPosInSet(const AXNode& node, const AXNode* ordered_set) {
  if (ordered_set_info_map_.find(node.id()) == ordered_set_info_map_.end())
    ComputeSetSizePosInSetAndCache(node, ordered_set);
  return ordered_set_info_map_[node.id()].pos_in_set;
}
