Fix position reporting during ads when period has non-zero window offset.

Reporting incorrect positions for ad playbacks was causing IMA to
think the ad wasn't playing, when in fact it was.

Issue: #3180

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=167702032

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

@@ -430,7 +430,9 @@ public final class ImaAdsLoader implements Player.EventListener, VideoAdPlayer,
     } else if (!playingAd) {
     } else if (!playingAd) {
       return VideoProgressUpdate.VIDEO_TIME_NOT_READY;
       return VideoProgressUpdate.VIDEO_TIME_NOT_READY;
     } else {
     } else {
-      return new VideoProgressUpdate(player.getCurrentPosition(), player.getDuration());
+      long adDuration = player.getDuration();
+      return adDuration == C.TIME_UNSET ? VideoProgressUpdate.VIDEO_TIME_NOT_READY
+          : new VideoProgressUpdate(player.getCurrentPosition(), adDuration);
     }
     }
   }
   }
 
 

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -319,8 +319,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
     if (timeline.isEmpty() || pendingSeekAcks > 0) {
     if (timeline.isEmpty() || pendingSeekAcks > 0) {
       return maskingWindowPositionMs;
       return maskingWindowPositionMs;
     } else {
     } else {
-      timeline.getPeriod(playbackInfo.periodId.periodIndex, period);
-      return period.getPositionInWindowMs() + C.usToMs(playbackInfo.positionUs);
+      return playbackInfoPositionUsToWindowPositionMs(playbackInfo.positionUs);
     }
     }
   }
   }
 
 
@@ -330,8 +329,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
     if (timeline.isEmpty() || pendingSeekAcks > 0) {
     if (timeline.isEmpty() || pendingSeekAcks > 0) {
       return maskingWindowPositionMs;
       return maskingWindowPositionMs;
     } else {
     } else {
-      timeline.getPeriod(playbackInfo.periodId.periodIndex, period);
-      return period.getPositionInWindowMs() + C.usToMs(playbackInfo.bufferedPositionUs);
+      return playbackInfoPositionUsToWindowPositionMs(playbackInfo.bufferedPositionUs);
     }
     }
   }
   }
 
 
@@ -358,7 +356,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
 
   @Override
   @Override
   public boolean isPlayingAd() {
   public boolean isPlayingAd() {
-    return pendingSeekAcks == 0 && playbackInfo.periodId.adGroupIndex != C.INDEX_UNSET;
+    return pendingSeekAcks == 0 && playbackInfo.periodId.isAd();
   }
   }
 
 
   @Override
   @Override
@@ -512,4 +510,13 @@ import java.util.concurrent.CopyOnWriteArraySet;
     }
     }
   }
   }
 
 
+  private long playbackInfoPositionUsToWindowPositionMs(long positionUs) {
+    long positionMs = C.usToMs(positionUs);
+    if (!playbackInfo.periodId.isAd()) {
+      timeline.getPeriod(playbackInfo.periodId.periodIndex, period);
+      positionMs += period.getPositionInWindowMs();
+    }
+    return positionMs;
+  }
+
 }
 }