Return whether an AXTree has a focused node or not

++
bool AXPlatformNodeAuraLinux::HasFocusableChild() {
  for (int i = 0; i < GetChildCount(); ++i) {
    if (GetChild(i)->IsIgnored() || GetChild(i)->IsChildOfLeaf())
      continue;
    if (GetChild(i)->IsDescendantOfLeaf())
      return true;
  }
  return false;
}