Return a bounding box of the link view.

If opt.useModelGeometry option is set to true, the resulting bounding box is calculated based on the dimensions of the link model. (This means that a simplified polyline is used and portions of curved links may be sticking out of the reported bounding box.) This behavior is similar to the link.getBBox function – but the linkView function transforms the bounding box to match joint.dia.Paper translation and scaling.