targetPaintedY property
Sliver-local painted y of targetKey's row at resolve time: the
space RenderSliverTree.findRowAtPaintedY speaks (first tree row at
0, including any active FLIP slide delta). Convert to viewport scroll
space by adding the tree sliver's precedingScrollExtent
(ReorderRenderPort.precedingScrollExtent).
Implementation
final double targetPaintedY;