Fix NPE when adding window with policy to hide

WindowState will be created with token. But it may not add
to the token immediately. So at that path it should use
getDisplayContent() that use token to get display.

Such as addWindow -> initAppOpsState -> setAppOpVisibilityLw
-> hide -> startAnimation.

"win.mToken.addWindow(win)" executes after that.

Bug: 226259929
Test: switch user
Change-Id: Ieba9df3bca87d10cd031d25e0b7f1e9a0c311dee