Enable PiP for top task before calling WCT#reorder,

When a task is moved to top via WCT#reorder, the task is moved
directly via WC#positionChildAt(), which bypasses the preparation
logic needed for an app behind to enter PiP.

Bug: 327233652
Test: Manual. Apps can enter PiP when another app is moved to top.
Change-Id: Ia2c50af741f12b4768f614cb77d06a4350cdf86f
1 file changed