PlacementControllerState
Read-only snapshot of a PlacementController’s state.
Properties
Section titled “Properties”exposureBasis
Section titled “exposureBasis”
readonlyexposureBasis:ExposureBasis|null
How the placement’s visual root came to be considered exposed, or null
before PlacementController.markVisible is called (plan 144 TASK-9).
'render_fallback' when IntersectionObserver was unavailable (AC-10).