Remove AdsManager listeners on release

Issue: #6687
PiperOrigin-RevId: 283023548

RELEASENOTES.md

@@ -140,6 +140,9 @@
     [Cast demo app](https://github.com/google/ExoPlayer/tree/dev-v2/demos/cast).
 * TestUtils: Publish the `testutils` module to simplify unit testing with
   ExoPlayer ([#6267](https://github.com/google/ExoPlayer/issues/6267)).
+* IMA extension: Remove `AdsManager` listeners on release to avoid leaking an
+  `AdEventListener` provided by the app
+  ([#6687](https://github.com/google/ExoPlayer/issues/6687)).
 
 ### 2.10.8 (2019-11-19) ###
 

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java

@@ -646,6 +646,11 @@ public final class ImaAdsLoader
   public void release() {
     pendingAdRequestContext = null;
     if (adsManager != null) {
+      adsManager.removeAdErrorListener(this);
+      adsManager.removeAdEventListener(this);
+      if (adEventListener != null) {
+        adsManager.removeAdEventListener(adEventListener);
+      }
       adsManager.destroy();
       adsManager = null;
     }