Run an app, where table is in single-cell multiple selection mode.

0. Click at cell (0,0).
1. Ctrl+down.
Selection : (0,0), focus : (0, 1)
2. Space
Selection : (0,0) (0, 1), focus : (0, 1)
3. Shift+down
Selection : (0,0) (0,1) (0,2)
But expected to be (0,1) (0,2)

So, anchor was not created for (0,1).

Affected tests:
ControlsAutomatedTestSuite/javafx/scene/control/test/tableview/TableViewMultipleCellSelectionTest/testSpaceWithModifiers
ControlsAutomatedTestSuite/javafx/scene/control/test/treetable/TreeTableMultipleSelectionTest/testSpaceWithModifiers


Issue has appeared now, because RT-27854 and RT-27816 were resolved as cannot reproduce recently, and were hiding this failure.