code: public void adoptParent(ElementBox parent)
      {
          if (parent instanceof BlockBox)
              setContainingBlockBox(parent);
          else
              setContainingBlockBox(parent.getContainingBlockBox());
          setParent(parent);
          setViewport(parent.getViewport());
          setClipBlock(parent.getClipBlock());
      }
docs: Initializes a box in order to be a proper child box of the specified parent. Copies
  all the necessary information from the parent.
  @param parent the parent box