code: public LockedInodePath lockChild(Inode child, LockPattern lockPattern,
        String[] childComponentsHint) throws InvalidPathException {
      LockedInodePath path = new LockedInodePath(mUri.joinUnsafe(child.getName()), this,
          childComponentsHint, lockPattern);
      path.traverseOrClose();
      return path;
    }
docs: Efficient version of {@link #lockChild(Inode, LockPattern)} for when the child path
  components are already known.
  
  @param child the child inode
  @param lockPattern the lock pattern
  @param childComponentsHint path components for the new path
  @return the new locked path