Hierarchy v2: entering fullscreen and exiting Play Mode hang the Editor while the Hierarchy is open

Steps to reproduce:

  1. Create a new project with Unity 6.7a4.

  2. Import the Bunny Blitz sample (no other packages or extensions).

  3. Open the project with the default layout (Hierarchy attached/docked).

  4. Enter Play Mode, then press the fullscreen shortcut (or right-click the Game view tab → Maximize) on the Game view.

    - Expected: Game view goes fullscreen immediately.

    - Actual: Editor stalls for several seconds before the fullscreen transition completes.

  5. Exit Play Mode.

    - Expected: Instant return to Edit Mode.

    - Actual: Editor stalls for several seconds.

Reproducible with versions: 

6.7a4

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): mac

Notes:

• CASE IN-150997