Allow resetting of position when setting source

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129083335

demo/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -125,6 +125,7 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
   private DebugTextViewHelper debugViewHelper;
   private boolean playerNeedsSource;
 
+  private boolean shouldRestorePosition;
   private int playerPeriodIndex;
   private long playerPosition;
 
@@ -278,7 +279,9 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
       player.setTextOutput(subtitleView);
       player.setVideoListener(this);
       player.setVideoSurfaceHolder(surfaceView.getHolder());
-      player.seekTo(playerPeriodIndex, playerPosition);
+      if (shouldRestorePosition) {
+        player.seekTo(playerPeriodIndex, playerPosition);
+      }
       player.setPlayWhenReady(true);
       mediaController.setMediaPlayer(new PlayerControl(player));
       mediaController.setPrevNextListeners(new MediaControllerPrevNextClickListener(player, true),
@@ -319,7 +322,7 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
       }
       MediaSource mediaSource = mediaSources.length == 1 ? mediaSources[0]
           : new ConcatenatingMediaSource(mediaSources);
-      player.setMediaSource(mediaSource);
+      player.setMediaSource(mediaSource, !shouldRestorePosition);
       playerNeedsSource = false;
       updateButtonVisibilities();
     }
@@ -368,6 +371,8 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
       debugViewHelper = null;
       playerPeriodIndex = player.getCurrentPeriodIndex();
       playerPosition = player.getCurrentPosition();
+      Timeline playerTimeline = player.getCurrentTimeline();
+      shouldRestorePosition = playerTimeline != null && playerTimeline.isFinal();
       player.release();
       player = null;
       trackSelector = null;

library/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -246,12 +246,20 @@ public interface ExoPlayer {
    */
   int getPlaybackState();
 
+  /**
+   * Sets the {@link MediaSource} to play. Equivalent to {@code setMediaSource(mediaSource, true)}.
+   */
+  void setMediaSource(MediaSource mediaSource);
+
   /**
    * Sets the {@link MediaSource} to play.
    *
    * @param mediaSource The {@link MediaSource} to play.
+   * @param resetPosition Whether the playback position should be reset to the source's default
+   *     position. If false, playback will start from the position defined by
+   *     {@link #getCurrentPeriodIndex()} and {@link #getCurrentPosition()}.
    */
-  void setMediaSource(MediaSource mediaSource);
+  void setMediaSource(MediaSource mediaSource, boolean resetPosition);
 
   /**
    * Sets whether playback should proceed when {@link #getPlaybackState()} == {@link #STATE_READY}.

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

@@ -97,8 +97,13 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void setMediaSource(MediaSource mediaSource) {
+    setMediaSource(mediaSource, true);
+  }
+
+  @Override
+  public void setMediaSource(MediaSource mediaSource, boolean resetPosition) {
     timeline = null;
-    internalPlayer.setMediaSource(mediaSource);
+    internalPlayer.setMediaSource(mediaSource, resetPosition);
   }
 
   @Override
@@ -140,7 +145,6 @@ import java.util.concurrent.CopyOnWriteArraySet;
     maskingPeriodIndex = periodIndex;
     maskingPositionMs = seekToDefaultPosition ? 0 : positionMs;
     maskingDurationMs = periodChanging ? ExoPlayer.UNKNOWN_TIME : getDuration();
-
     pendingSeekAcks++;
     internalPlayer.seekTo(periodIndex, seekToDefaultPosition ? C.UNSET_TIME_US : positionMs * 1000);
     if (!seekToDefaultPosition) {

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

@@ -152,8 +152,9 @@ import java.util.ArrayList;
     handler = new Handler(internalPlaybackThread.getLooper(), this);
   }
 
-  public void setMediaSource(MediaSource mediaSource) {
+  public void setMediaSource(MediaSource mediaSource, boolean resetPosition) {
-    handler.obtainMessage(MSG_SET_MEDIA_SOURCE, mediaSource).sendToTarget();
+    handler.obtainMessage(MSG_SET_MEDIA_SOURCE, resetPosition ? 1 : 0, 0, mediaSource)
+        .sendToTarget();
   }
 
   public void setPlayWhenReady(boolean playWhenReady) {
@@ -161,7 +162,7 @@ import java.util.ArrayList;
   }
 
   public void seekTo(int periodIndex, long positionUs) {
-    handler.obtainMessage(MSG_SEEK_TO, periodIndex, -1, positionUs).sendToTarget();
+    handler.obtainMessage(MSG_SEEK_TO, periodIndex, 0, positionUs).sendToTarget();
   }
 
   public void stop() {
@@ -234,7 +235,7 @@ import java.util.ArrayList;
     try {
       switch (msg.what) {
         case MSG_SET_MEDIA_SOURCE: {
-          setMediaSourceInternal((MediaSource) msg.obj);
+          setMediaSourceInternal((MediaSource) msg.obj, msg.arg1 != 0);
           return true;
         }
         case MSG_SET_PLAY_WHEN_READY: {
@@ -328,8 +329,14 @@ import java.util.ArrayList;
     }
   }
 
-  private void setMediaSourceInternal(MediaSource mediaSource) {
+  private void setMediaSourceInternal(MediaSource mediaSource, boolean resetPosition)
+      throws ExoPlaybackException {
     resetInternal();
+    if (resetPosition) {
+      playbackInfo = new PlaybackInfo(0);
+      playbackInfo.startPositionUs = C.UNSET_TIME_US;
+      playbackInfo.positionUs = C.UNSET_TIME_US;
+    }
     this.mediaSource = mediaSource;
     mediaSource.prepareSource(this);
     setState(ExoPlayer.STATE_BUFFERING);

library/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java

@@ -329,6 +329,11 @@ public final class SimpleExoPlayer implements ExoPlayer {
     player.setMediaSource(mediaSource);
   }
 
+  @Override
+  public void setMediaSource(MediaSource mediaSource, boolean resetPosition) {
+    player.setMediaSource(mediaSource, resetPosition);
+  }
+
   @Override
   public void setPlayWhenReady(boolean playWhenReady) {
     player.setPlayWhenReady(playWhenReady);