Fix for SysUi overrides being applied on non-fullscreen VIS windows.

See the attached bug for a detailed explanation of the issue.
For Android reviewers: please confirm that this change will also make it to the Pixel 6 System Image.

Test: manually, by updating the height of the decor view, and observing behavior with and without applying sysui flags to it
Bug: 190027393
Change-Id: Ia5933424e33c424cf642131923aed4fe624c52d3