Fix a bug where the tiling divider isn't drawn when snapping to same pos.

When the user snaps an app through app header to the same tiling position,
the snapping animation won't be triggered, and the animation callback that
draws the divider won't be called.

This CL ensures the divider is drawn in this corner case.

Flag: com.android.window.flags.enable_tile_resizing

Test: On device testing, logic to draw UI is private and can't be tested.

Bug: 402098695
Change-Id: I11d2279842c7eafc04d2f0f806904ccee6aced71