Fix restoring of position.

This change restores ExoPlayer to its previous behaviour.
I think we'll want a "resetPosition" boolean parameter on
setMediaSource at some point, but no need to add it right
now. Note that this would not always reset to the start
of the source. For a live playback it will reset to the
desired position (normally somewhere slightly behind the
live edge).

Issue: #1667
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=127549700

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

@@ -137,6 +137,7 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
   private BandwidthMeter bandwidthMeter;
   private boolean playerNeedsSource;
 
+  private int playerPeriodIndex;
   private long playerPosition;
 
   // Activity lifecycle
@@ -286,7 +287,7 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
       player.setVideoListener(this);
       player.setCaptionListener(this);
       player.setMetadataListener(this);
-      player.seekTo(playerPosition);
+      player.seekTo(playerPeriodIndex, playerPosition);
       player.setSurface(surfaceView.getHolder().getSurface());
       player.setPlayWhenReady(true);
       mediaController.setMediaPlayer(new PlayerControl(player));
@@ -406,6 +407,7 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
       shutterView.setVisibility(View.VISIBLE);
       debugViewHelper.stop();
       debugViewHelper = null;
+      playerPeriodIndex = player.getCurrentPeriodIndex();
       playerPosition = player.getCurrentPosition();
       player.release();
       player = null;

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

@@ -240,8 +240,6 @@ public interface ExoPlayer {
 
   /**
    * Sets the {@link MediaSource} to play.
-   * <p>
-   * The player's position will be reset to the start of the source.
    *
    * @param mediaSource The {@link MediaSource} to play.
    */

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

@@ -42,7 +42,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
   private boolean playWhenReady;
   private int playbackState;
   private int pendingPlayWhenReadyAcks;
-  private int pendingSetMediaSourceAndSeekAcks;
+  private int pendingSeekAcks;
   private boolean isLoading;
 
   // Playback information when there is no pending seek/set source operation.
@@ -97,15 +97,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void setMediaSource(MediaSource mediaSource) {
-    maskingPeriodIndex = 0;
-    maskingPositionMs = 0;
-    maskingDurationMs = ExoPlayer.UNKNOWN_TIME;
-
-    pendingSetMediaSourceAndSeekAcks++;
     internalPlayer.setMediaSource(mediaSource);
-    for (EventListener listener : listeners) {
-      listener.onPositionDiscontinuity(0, 0);
-    }
   }
 
   @Override
@@ -147,7 +139,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
     maskingPositionMs = positionMs;
     maskingDurationMs = periodChanging ? ExoPlayer.UNKNOWN_TIME : getDuration();
 
-    pendingSetMediaSourceAndSeekAcks++;
+    pendingSeekAcks++;
     internalPlayer.seekTo(periodIndex, positionMs * 1000);
     for (EventListener listener : listeners) {
       listener.onPositionDiscontinuity(periodIndex, positionMs);
@@ -177,7 +169,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public long getDuration() {
-    if (pendingSetMediaSourceAndSeekAcks == 0) {
+    if (pendingSeekAcks == 0) {
       long durationUs = playbackInfo.durationUs;
       return durationUs == C.UNSET_TIME_US ? ExoPlayer.UNKNOWN_TIME : durationUs / 1000;
     } else {
@@ -187,18 +179,18 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public long getCurrentPosition() {
-    return pendingSetMediaSourceAndSeekAcks == 0 ? playbackInfo.positionUs / 1000
+    return pendingSeekAcks == 0 ? playbackInfo.positionUs / 1000
         : maskingPositionMs;
   }
 
   @Override
   public int getCurrentPeriodIndex() {
-    return pendingSetMediaSourceAndSeekAcks == 0 ? playbackInfo.periodIndex : maskingPeriodIndex;
+    return pendingSeekAcks == 0 ? playbackInfo.periodIndex : maskingPeriodIndex;
   }
 
   @Override
   public long getBufferedPosition() {
-    if (pendingSetMediaSourceAndSeekAcks == 0) {
+    if (pendingSeekAcks == 0) {
       long bufferedPositionUs = playbackInfo.bufferedPositionUs;
       return bufferedPositionUs == C.END_OF_SOURCE_US ? getDuration() : bufferedPositionUs / 1000;
     } else {
@@ -240,14 +232,13 @@ import java.util.concurrent.CopyOnWriteArraySet;
         }
         break;
       }
-      case ExoPlayerImplInternal.MSG_SET_MEDIA_SOURCE_ACK: // Fall through.
       case ExoPlayerImplInternal.MSG_SEEK_ACK: {
-        pendingSetMediaSourceAndSeekAcks--;
+        pendingSeekAcks--;
         break;
       }
       case ExoPlayerImplInternal.MSG_PERIOD_CHANGED: {
         playbackInfo = (ExoPlayerImplInternal.PlaybackInfo) msg.obj;
-        if (pendingSetMediaSourceAndSeekAcks == 0) {
+        if (pendingSeekAcks == 0) {
           for (EventListener listener : listeners) {
             listener.onPositionDiscontinuity(playbackInfo.periodIndex, 0);
           }

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

@@ -72,10 +72,9 @@ import java.util.ArrayList;
   public static final int MSG_STATE_CHANGED = 1;
   public static final int MSG_LOADING_CHANGED = 2;
   public static final int MSG_SET_PLAY_WHEN_READY_ACK = 3;
-  public static final int MSG_SET_MEDIA_SOURCE_ACK = 4;
-  public static final int MSG_SEEK_ACK = 5;
-  public static final int MSG_PERIOD_CHANGED = 6;
-  public static final int MSG_ERROR = 7;
+  public static final int MSG_SEEK_ACK = 4;
+  public static final int MSG_PERIOD_CHANGED = 5;
+  public static final int MSG_ERROR = 6;
 
   // Internal messages
   private static final int MSG_SET_MEDIA_SOURCE = 0;
@@ -311,15 +310,11 @@ import java.util.ArrayList;
   }
 
   private void setMediaSourceInternal(MediaSource mediaSource) {
-    try {
-      resetInternal();
-      this.mediaSource = mediaSource;
-      mediaSource.prepareSource();
-      setState(ExoPlayer.STATE_BUFFERING);
-      handler.sendEmptyMessage(MSG_DO_SOME_WORK);
-    } finally {
-      eventHandler.sendEmptyMessage(MSG_SET_MEDIA_SOURCE_ACK);
-    }
+    resetInternal();
+    this.mediaSource = mediaSource;
+    mediaSource.prepareSource();
+    setState(ExoPlayer.STATE_BUFFERING);
+    handler.sendEmptyMessage(MSG_DO_SOME_WORK);
   }
 
   private void setPlayWhenReadyInternal(boolean playWhenReady) throws ExoPlaybackException {
@@ -596,7 +591,6 @@ import java.util.ArrayList;
     private Period readingPeriod;
     private Period loadingPeriod;
 
-    private int pendingPeriodIndex;
     private long playingPeriodEndPositionUs;
 
     public Timeline(Renderer[] renderers) {
@@ -651,7 +645,8 @@ import java.util.ArrayList;
           || (loadingPeriod.isFullyBuffered() && loadingPeriod.index
               - (playingPeriod != null ? playingPeriod.index : 0) < MAXIMUM_BUFFER_AHEAD_SOURCES)) {
         // Try and obtain the next period to start loading.
-        int periodIndex = loadingPeriod == null ? pendingPeriodIndex : loadingPeriod.index + 1;
+        int periodIndex = loadingPeriod == null ? playbackInfo.periodIndex
+            : loadingPeriod.index + 1;
         if (periodCount == MediaSource.UNKNOWN_PERIOD_COUNT || periodIndex < periodCount) {
           // Attempt to create the next period.
           MediaPeriod mediaPeriod = mediaSource.createPeriod(periodIndex);
@@ -817,7 +812,6 @@ import java.util.ArrayList;
         playingPeriod = null;
         readingPeriod = null;
         loadingPeriod = null;
-        pendingPeriodIndex = periodIndex;
         resetInternalPosition(seekPositionUs);
       }
       return seekPositionUs;
@@ -911,14 +905,12 @@ import java.util.ArrayList;
         period.release();
         period = period.nextPeriod;
       }
+      playingPeriodEndPositionUs = C.UNSET_TIME_US;
       isReady = false;
       isEnded = false;
       playingPeriod = null;
       readingPeriod = null;
       loadingPeriod = null;
-      playingPeriodEndPositionUs = C.UNSET_TIME_US;
-      pendingPeriodIndex = 0;
-      playbackInfo = new PlaybackInfo(0);
       eventHandler.obtainMessage(MSG_PERIOD_CHANGED, playbackInfo).sendToTarget();
     }