Support resuming ads

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=161778560

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

@@ -51,6 +51,11 @@ import java.util.Arrays;
    */
   public final Uri[][] adUris;
 
+  /**
+   * The position offset in the first unplayed ad at which to begin playback, in microseconds.
+   */
+  public long adResumePositionUs;
+
   /**
    * Creates a new ad playback state with the specified ad group times.
    *
@@ -69,12 +74,13 @@ import java.util.Arrays;
   }
 
   private AdPlaybackState(long[] adGroupTimesUs, int[] adCounts, int[] adsLoadedCounts,
-      int[] adsPlayedCounts, Uri[][] adUris) {
+      int[] adsPlayedCounts, Uri[][] adUris, long adResumePositionUs) {
     this.adGroupTimesUs = adGroupTimesUs;
     this.adCounts = adCounts;
     this.adsLoadedCounts = adsLoadedCounts;
     this.adsPlayedCounts = adsPlayedCounts;
     this.adUris = adUris;
+    this.adResumePositionUs = adResumePositionUs;
     adGroupCount = adGroupTimesUs.length;
   }
 
@@ -87,10 +93,8 @@ import java.util.Arrays;
       adUris[i] = Arrays.copyOf(this.adUris[i], this.adUris[i].length);
     }
     return new AdPlaybackState(Arrays.copyOf(adGroupTimesUs, adGroupCount),
-        Arrays.copyOf(adCounts, adGroupCount),
-        Arrays.copyOf(adsLoadedCounts, adGroupCount),
-        Arrays.copyOf(adsPlayedCounts, adGroupCount),
-        adUris);
+        Arrays.copyOf(adCounts, adGroupCount), Arrays.copyOf(adsLoadedCounts, adGroupCount),
+        Arrays.copyOf(adsPlayedCounts, adGroupCount), adUris, adResumePositionUs);
   }
 
   /**
@@ -114,7 +118,15 @@ import java.util.Arrays;
    * Marks the last ad in the specified ad group as played.
    */
   public void playedAd(int adGroupIndex) {
+    adResumePositionUs = 0;
     adsPlayedCounts[adGroupIndex]++;
   }
 
+  /**
+   * Sets the position offset in the first unplayed ad at which to begin playback, in microseconds.
+   */
+  public void setAdResumePositionUs(long adResumePositionUs) {
+    this.adResumePositionUs = adResumePositionUs;
+  }
+
 }

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

@@ -226,7 +226,9 @@ public final class ImaAdsLoader implements ExoPlayer.EventListener, VideoAdPlaye
     player.addListener(this);
     if (adPlaybackState != null) {
       eventListener.onAdPlaybackState(adPlaybackState);
-      // TODO: Call adsManager.resume if an ad is playing.
+      if (playingAd) {
+        adsManager.resume();
+      }
     } else if (adTagUri != null) {
       requestAds();
     }
@@ -239,7 +241,8 @@ public final class ImaAdsLoader implements ExoPlayer.EventListener, VideoAdPlaye
    */
   /* package */ void detachPlayer() {
     if (player != null) {
-      if (adsManager != null && player.isPlayingAd()) {
+      if (adsManager != null && playingAd) {
+        adPlaybackState.setAdResumePositionUs(C.msToUs(player.getCurrentPosition()));
         adsManager.pause();
       }
       lastAdProgress = getAdProgress();
@@ -449,12 +452,14 @@ public final class ImaAdsLoader implements ExoPlayer.EventListener, VideoAdPlaye
     if (DEBUG) {
       Log.d(TAG, "pauseAd");
     }
-    if (player == null || !imaPlayingAd) {
-      // This method is called after content is resumed, and may also be called after release.
+    if (!imaPlayingAd) {
+      // This method is called after content is resumed.
       return;
     }
     imaPausedInAd = true;
-    player.setPlayWhenReady(false);
+    if (player != null) {
+      player.setPlayWhenReady(false);
+    }
     for (VideoAdPlayerCallback callback : adCallbacks) {
       callback.onPause();
     }

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

@@ -210,7 +210,7 @@ public final class ImaAdsMediaSource implements MediaSource {
     if (adPlaybackState != null && contentTimeline != null) {
       SinglePeriodAdTimeline timeline = new SinglePeriodAdTimeline(contentTimeline,
           adPlaybackState.adGroupTimesUs, adPlaybackState.adCounts, adPlaybackState.adsLoadedCounts,
-          adPlaybackState.adsPlayedCounts, adDurationsUs);
+          adPlaybackState.adsPlayedCounts, adDurationsUs, adPlaybackState.adResumePositionUs);
       listener.onSourceInfoRefreshed(timeline, contentManifest);
     }
   }

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

@@ -30,6 +30,7 @@ public final class SinglePeriodAdTimeline extends Timeline {
   private final int[] adsLoadedCounts;
   private final int[] adsPlayedCounts;
   private final long[][] adDurationsUs;
+  private final long adResumePositionUs;
 
   /**
    * Creates a new timeline with a single period containing the specified ads.
@@ -45,9 +46,12 @@ public final class SinglePeriodAdTimeline extends Timeline {
    * @param adsPlayedCounts The number of ads played so far in each ad group.
    * @param adDurationsUs The duration of each ad in each ad group, in microseconds. An element
    *     may be {@link C#TIME_UNSET} if the duration is not yet known.
+   * @param adResumePositionUs The position offset in the earliest unplayed ad at which to begin
+   *     playback, in microseconds.
    */
   public SinglePeriodAdTimeline(Timeline contentTimeline, long[] adGroupTimesUs, int[] adCounts,
-      int[] adsLoadedCounts, int[] adsPlayedCounts, long[][] adDurationsUs) {
+      int[] adsLoadedCounts, int[] adsPlayedCounts, long[][] adDurationsUs,
+      long adResumePositionUs) {
     Assertions.checkState(contentTimeline.getPeriodCount() == 1);
     Assertions.checkState(contentTimeline.getWindowCount() == 1);
     this.contentTimeline = contentTimeline;
@@ -56,6 +60,7 @@ public final class SinglePeriodAdTimeline extends Timeline {
     this.adsLoadedCounts = adsLoadedCounts;
     this.adsPlayedCounts = adsPlayedCounts;
     this.adDurationsUs = adDurationsUs;
+    this.adResumePositionUs = adResumePositionUs;
   }
 
   @Override
@@ -79,7 +84,7 @@ public final class SinglePeriodAdTimeline extends Timeline {
     contentTimeline.getPeriod(periodIndex, period, setIds);
     period.set(period.id, period.uid, period.windowIndex, period.durationUs,
         period.getPositionInWindowUs(), adGroupTimesUs, adCounts, adsLoadedCounts, adsPlayedCounts,
-        adDurationsUs);
+        adDurationsUs, adResumePositionUs);
     return period;
   }
 

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

@@ -300,8 +300,10 @@ import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
     boolean isLastInTimeline = isLastInTimeline(id, isLastInPeriod);
     long durationUs = timeline.getPeriod(id.periodIndex, period)
         .getAdDurationUs(id.adGroupIndex, id.adIndexInAdGroup);
-    return new MediaPeriodInfo(id, 0, C.TIME_END_OF_SOURCE, contentPositionUs, durationUs,
-        isLastInPeriod, isLastInTimeline);
+    long startPositionUs = adIndexInAdGroup == period.getPlayedAdCount(adGroupIndex)
+        ? period.getAdResumePositionUs() : 0;
+    return new MediaPeriodInfo(id, startPositionUs, C.TIME_END_OF_SOURCE, contentPositionUs,
+        durationUs, isLastInPeriod, isLastInTimeline);
   }
 
   private MediaPeriodInfo getMediaPeriodInfoForContent(int periodIndex, long startPositionUs,

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

@@ -270,6 +270,7 @@ public abstract class Timeline {
     private int[] adsLoadedCounts;
     private int[] adsPlayedCounts;
     private long[][] adDurationsUs;
+    private long adResumePositionUs;
 
     /**
      * Sets the data held by this period.
@@ -287,7 +288,7 @@ public abstract class Timeline {
     public Period set(Object id, Object uid, int windowIndex, long durationUs,
         long positionInWindowUs) {
       return set(id, uid, windowIndex, durationUs, positionInWindowUs, null, null, null, null,
-          null);
+          null, C.TIME_UNSET);
     }
 
     /**
@@ -310,11 +311,13 @@ public abstract class Timeline {
      * @param adsPlayedCounts The number of ads played so far in each ad group.
      * @param adDurationsUs The duration of each ad in each ad group, in microseconds. An element
      *     may be {@link C#TIME_UNSET} if the duration is not yet known.
+     * @param adResumePositionUs The position offset in the first unplayed ad at which to begin
+     *     playback, in microseconds.
      * @return This period, for convenience.
      */
     public Period set(Object id, Object uid, int windowIndex, long durationUs,
         long positionInWindowUs, long[] adGroupTimesUs, int[] adCounts, int[] adsLoadedCounts,
-        int[] adsPlayedCounts, long[][] adDurationsUs) {
+        int[] adsPlayedCounts, long[][] adDurationsUs, long adResumePositionUs) {
       this.id = id;
       this.uid = uid;
       this.windowIndex = windowIndex;
@@ -325,6 +328,7 @@ public abstract class Timeline {
       this.adsLoadedCounts = adsLoadedCounts;
       this.adsPlayedCounts = adsPlayedCounts;
       this.adDurationsUs = adDurationsUs;
+      this.adResumePositionUs = adResumePositionUs;
       return this;
     }
 
@@ -479,6 +483,14 @@ public abstract class Timeline {
       return adDurationsUs[adGroupIndex][adIndexInAdGroup];
     }
 
+    /**
+     * Returns the position offset in the first unplayed ad at which to begin playback, in
+     * microseconds.
+     */
+    public long getAdResumePositionUs() {
+      return adResumePositionUs;
+    }
+
   }
 
   /**