Fix handling of ad tags with only preroll and postroll ads

Content progress is only polled if there are midroll ad groups. If the ad tag
had only preroll/postroll ads, the pending content position was not provided to
IMA, which meant that the postroll ad could never play.

Only set the pending content position if there are midroll ads.

Issue: #3715

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=185680803

RELEASENOTES.md

@@ -97,6 +97,8 @@
       ([#3676](https://github.com/google/ExoPlayer/issues/3676)).
       ([#3676](https://github.com/google/ExoPlayer/issues/3676)).
     * Fix handling of ad tags where ad groups are out of order
     * Fix handling of ad tags where ad groups are out of order
       ([#3716](https://github.com/google/ExoPlayer/issues/3716)).
       ([#3716](https://github.com/google/ExoPlayer/issues/3716)).
+    * Fix handling of ad tags with only preroll/postroll ad groups
+      ([#3715](https://github.com/google/ExoPlayer/issues/3715)).
     * Propagate ad media preparation errors to IMA so that the ads can be
     * Propagate ad media preparation errors to IMA so that the ads can be
       skipped.
       skipped.
 * `EventLogger` moved from the demo app into the core library.
 * `EventLogger` moved from the demo app into the core library.

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

@@ -851,15 +851,14 @@ public final class ImaAdsLoader extends Player.DefaultEventListener implements A
     adsRenderingSettings.setMimeTypes(supportedMimeTypes);
     adsRenderingSettings.setMimeTypes(supportedMimeTypes);
 
 
     // Set up the ad playback state, skipping ads based on the start position as required.
     // Set up the ad playback state, skipping ads based on the start position as required.
-    pendingContentPositionMs = player.getCurrentPosition();
     long[] adGroupTimesUs = getAdGroupTimesUs(adsManager.getAdCuePoints());
     long[] adGroupTimesUs = getAdGroupTimesUs(adsManager.getAdCuePoints());
     adPlaybackState = new AdPlaybackState(adGroupTimesUs);
     adPlaybackState = new AdPlaybackState(adGroupTimesUs);
+    long contentPositionMs = player.getCurrentPosition();
     int adGroupIndexForPosition =
     int adGroupIndexForPosition =
-        adPlaybackState.getAdGroupIndexForPositionUs(C.msToUs(pendingContentPositionMs));
+        adPlaybackState.getAdGroupIndexForPositionUs(C.msToUs(contentPositionMs));
     if (adGroupIndexForPosition == 0) {
     if (adGroupIndexForPosition == 0) {
       podIndexOffset = 0;
       podIndexOffset = 0;
     } else if (adGroupIndexForPosition == C.INDEX_UNSET) {
     } else if (adGroupIndexForPosition == C.INDEX_UNSET) {
-      pendingContentPositionMs = C.TIME_UNSET;
       // There is no preroll and midroll pod indices start at 1.
       // There is no preroll and midroll pod indices start at 1.
       podIndexOffset = -1;
       podIndexOffset = -1;
     } else /* adGroupIndexForPosition > 0 */ {
     } else /* adGroupIndexForPosition > 0 */ {
@@ -879,6 +878,11 @@ public final class ImaAdsLoader extends Player.DefaultEventListener implements A
       podIndexOffset = adGroupIndexForPosition - 1;
       podIndexOffset = adGroupIndexForPosition - 1;
     }
     }
 
 
+    if (hasMidrollAdGroups(adGroupTimesUs)) {
+      // IMA will poll the content position, so provide the player's initial position like a seek.
+      pendingContentPositionMs = contentPositionMs;
+    }
+
     // Start ad playback.
     // Start ad playback.
     adsManager.init(adsRenderingSettings);
     adsManager.init(adsRenderingSettings);
     updateAdPlaybackState();
     updateAdPlaybackState();
@@ -1051,4 +1055,16 @@ public final class ImaAdsLoader extends Player.DefaultEventListener implements A
     // a single ad, ad group or the whole timeline.
     // a single ad, ad group or the whole timeline.
     return adError.getErrorCode() == AdErrorCode.VAST_LINEAR_ASSET_MISMATCH;
     return adError.getErrorCode() == AdErrorCode.VAST_LINEAR_ASSET_MISMATCH;
   }
   }
+
+  private static boolean hasMidrollAdGroups(long[] adGroupTimesUs) {
+    int count = adGroupTimesUs.length;
+    if (count == 1) {
+      return adGroupTimesUs[0] != 0 && adGroupTimesUs[0] != C.TIME_END_OF_SOURCE;
+    } else if (count == 2) {
+      return adGroupTimesUs[0] != 0 || adGroupTimesUs[1] != C.TIME_END_OF_SOURCE;
+    } else {
+      // There's at least one midroll ad group, as adGroupTimesUs is never empty.
+      return true;
+    }
+  }
 }
 }