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}
AXTree::AXTree() {
  AXNodeData root;
  root.id = -1;

  AXTreeUpdate initial_state;
  initial_state.root_id = -1;
  initial_state.nodes.push_back(root);
  CHECK(Unserialize(initial_state)) << error();
}

AXTree::AXTree() {
  AXNodeData root;
  root.id = -1;

  AXTreeUpdate initial_state;
  initial_state.root_id = -1;
  initial_state.nodes.push_back(root);
  CHECK(Unserialize(initial_state)) << error();
}
