Add isControllerVisible

Issue: #4385

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=200986828

RELEASENOTES.md

@@ -31,6 +31,8 @@
   ([#4348](https://github.com/google/ExoPlayer/issues/4348)).
 * Fix issue when switching track selection from an embedded track to a primary
   track in DASH ([#4477](https://github.com/google/ExoPlayer/issues/4477)).
+* Add `PlayerView.isControllerVisible`
+  ([#4385](https://github.com/google/ExoPlayer/issues/4385)).
 
 ### 2.8.2 ###
 

library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java

@@ -696,6 +696,11 @@ public class PlayerView extends FrameLayout {
     return useController && controller.dispatchMediaKeyEvent(event);
   }
 
+  /** Returns whether the controller is currently visible. */
+  public boolean isControllerVisible() {
+    return controller != null && controller.isVisible();
+  }
+
   /**
    * Shows the playback controls. Does nothing if playback controls are disabled.
    *