Fix condition for detecting that an ad has ended

onEnded was being called also for content finishing, as in this case the playing
ad index changed (from INDEX_UNSET to 0). Fix this test so we only detect ads
finishing.

Also add logging for onEnded callbacks.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=179167737

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

@@ -702,6 +702,9 @@ public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
       for (int i = 0; i < adCallbacks.size(); i++) {
         adCallbacks.get(i).onEnded();
       }
+      if (DEBUG) {
+        Log.d(TAG, "VideoAdPlayerCallback.onEnded in onPlayerStateChanged");
+      }
     }
   }
 
@@ -797,16 +800,20 @@ private void maybeNotifyAdError() {
 
   private void updateImaStateForPlayerState() {
     boolean wasPlayingAd = playingAd;
+    int oldPlayingAdIndexInAdGroup = playingAdIndexInAdGroup;
     playingAd = player.isPlayingAd();
+    playingAdIndexInAdGroup = playingAd ? player.getCurrentAdIndexInAdGroup() : C.INDEX_UNSET;
     if (!sentContentComplete) {
-      boolean adFinished = (wasPlayingAd && !playingAd)
-          || playingAdIndexInAdGroup != player.getCurrentAdIndexInAdGroup();
+      boolean adFinished = wasPlayingAd && playingAdIndexInAdGroup != oldPlayingAdIndexInAdGroup;
       if (adFinished) {
         // IMA is waiting for the ad playback to finish so invoke the callback now.
         // Either CONTENT_RESUME_REQUESTED will be passed next, or playAd will be called again.
         for (int i = 0; i < adCallbacks.size(); i++) {
           adCallbacks.get(i).onEnded();
         }
+        if (DEBUG) {
+          Log.d(TAG, "VideoAdPlayerCallback.onEnded in onTimelineChanged/onPositionDiscontinuity");
+        }
       }
       if (!wasPlayingAd && playingAd) {
         int adGroupIndex = player.getCurrentAdGroupIndex();
@@ -818,7 +825,6 @@ private void updateImaStateForPlayerState() {
         }
       }
     }
-    playingAdIndexInAdGroup = playingAd ? player.getCurrentAdIndexInAdGroup() : C.INDEX_UNSET;
   }
 
   private void resumeContentInternal() {