Show last seek position when playing an ad

We'd normally expect playback controls to be hidden during
ad playback, although if they are visible for whatever reason,
it makes sense to set the position to the current content
position now that we have it.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=161950098

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

@@ -755,8 +755,11 @@ public class PlaybackControlView extends FrameLayout {
       }
       duration = C.usToMs(durationUs);
       position = C.usToMs(currentWindowTimeBarOffsetUs);
-      bufferedPosition = C.usToMs(currentWindowTimeBarOffsetUs);
-      if (!player.isPlayingAd()) {
+      bufferedPosition = position;
+      if (player.isPlayingAd()) {
+        position += player.getContentPosition();
+        bufferedPosition = position;
+      } else {
         position += player.getCurrentPosition();
         bufferedPosition += player.getBufferedPosition();
       }