AdOverlayInfo.Purpose (ExoPlayer library)

```
@Documented
@Retention(SOURCE)
@Target({FIELD,METHOD,PARAMETER,LOCAL_VARIABLE,TYPE_USE})
public static @interface AdOverlayInfo.Purpose
```
The purpose of the overlay. One of AdOverlayInfo.PURPOSE_CONTROLS, AdOverlayInfo.PURPOSE_CLOSE_AD, AdOverlayInfo.PURPOSE_OTHER or AdOverlayInfo.PURPOSE_NOT_VISIBLE.