Perform layout after removing the focused window

This change fixes a bug that navigation bar didn't show after the
hide-nav-bar window had been removed.

Bug: 81118995
Test: 1. go/wm-smoke
      2. a. Open an app which can show a window which hides nav bar.
         b. Make the app show the window which hides nav bar.
         c. Dismiss the window and see if nav bar shows.
      3. atest CtsWindowManagerDeviceTestCases:LayoutTests

Change-Id: I859b467b44bab8ea30dd5c4b03aa1673a30534fa