The 'alphabetic' (or 'roman') baseline offset from the node's layoutBounds.minY location that should be used when this node is being vertically aligned by baseline with other nodes. By default this returns BASELINE_OFFSET_SAME_AS_HEIGHT for resizable Nodes and layoutBounds height for non-resizable. Subclasses which contain text should override this method to return their actual text baseline offset.

Returns:  offset of text baseline from layoutBounds.minY for non-resizable Nodes or BASELINE_OFFSET_SAME_AS_HEIGHT otherwise