Add ad insertion discontinuity reason.

This it to distinguish between actual period transitions and the
transitions occuring to and from ads within one timeline period.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=181606023

RELEASENOTES.md

@@ -9,6 +9,10 @@
   * Add optional parameter to `stop` to reset the player when stopping.
   * Add a reason to `EventListener.onTimelineChanged` to distinguish between
     initial preparation, reset and dynamic updates.
+  * Add `Player.DISCONTINUITY_REASON_AD_INSERTION` to the possible reasons
+    reported in `Eventlistener.onPositionDiscontinuity` to distinguish
+    transitions to and from ads within one period from transitions between
+    periods.
   * Replaced `ExoPlayer.sendMessages` with `ExoPlayer.createMessage` to allow
     more customization of the message. Now supports setting a message delivery
     playback position and/or a delivery handler.

demos/main/src/main/java/com/google/android/exoplayer2/demo/EventLogger.java

@@ -528,6 +528,8 @@ import java.util.Locale;
         return "SEEK";
       case Player.DISCONTINUITY_REASON_SEEK_ADJUSTMENT:
         return "SEEK_ADJUSTMENT";
+      case Player.DISCONTINUITY_REASON_AD_INSERTION:
+        return "AD_INSERTION";
       case Player.DISCONTINUITY_REASON_INTERNAL:
         return "INTERNAL";
       default:

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

@@ -1448,11 +1448,15 @@ import java.util.Collections;
         // If we advance more than one period at a time, notify listeners after each update.
         maybeNotifyPlaybackInfoChanged();
       }
+      int discontinuityReason =
+          playingPeriodHolder.info.isLastInTimelinePeriod
+              ? Player.DISCONTINUITY_REASON_PERIOD_TRANSITION
+              : Player.DISCONTINUITY_REASON_AD_INSERTION;
       playingPeriodHolder.release();
       setPlayingPeriodHolder(playingPeriodHolder.next);
       playbackInfo = playbackInfo.fromNewPosition(playingPeriodHolder.info.id,
           playingPeriodHolder.info.startPositionUs, playingPeriodHolder.info.contentPositionUs);
-      playbackInfoUpdate.setPositionDiscontinuity(Player.DISCONTINUITY_REASON_PERIOD_TRANSITION);
+      playbackInfoUpdate.setPositionDiscontinuity(discontinuityReason);
       updatePlaybackPositions();
       advancedPlayingPeriod = true;
     }

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

@@ -251,31 +251,32 @@ public interface Player {
    */
   int REPEAT_MODE_ALL = 2;
 
-  /**
+  /** Reasons for position discontinuities. */
-   * Reasons for position discontinuities.
-   */
   @Retention(RetentionPolicy.SOURCE)
-  @IntDef({DISCONTINUITY_REASON_PERIOD_TRANSITION, DISCONTINUITY_REASON_SEEK,
+  @IntDef({
-      DISCONTINUITY_REASON_SEEK_ADJUSTMENT, DISCONTINUITY_REASON_INTERNAL})
+    DISCONTINUITY_REASON_PERIOD_TRANSITION,
+    DISCONTINUITY_REASON_SEEK,
+    DISCONTINUITY_REASON_SEEK_ADJUSTMENT,
+    DISCONTINUITY_REASON_AD_INSERTION,
+    DISCONTINUITY_REASON_INTERNAL
+  })
   public @interface DiscontinuityReason {}
   /**
    * Automatic playback transition from one period in the timeline to the next. The period index may
    * be the same as it was before the discontinuity in case the current period is repeated.
    */
   int DISCONTINUITY_REASON_PERIOD_TRANSITION = 0;
-  /**
+  /** Seek within the current period or to another period. */
-   * Seek within the current period or to another period.
-   */
   int DISCONTINUITY_REASON_SEEK = 1;
   /**
    * Seek adjustment due to being unable to seek to the requested position or because the seek was
    * permitted to be inexact.
    */
   int DISCONTINUITY_REASON_SEEK_ADJUSTMENT = 2;
-  /**
+  /** Discontinuity to or from an ad within one period in the timeline. */
-   * Discontinuity introduced internally by the source.
+  int DISCONTINUITY_REASON_AD_INSERTION = 3;
-   */
+  /** Discontinuity introduced internally by the source. */
-  int DISCONTINUITY_REASON_INTERNAL = 3;
+  int DISCONTINUITY_REASON_INTERNAL = 4;
 
   /**
    * Reasons for timeline and/or manifest changes.