Improve multi-window playback controls behavior.

Only enable multi-window mode when the duration of every period in the timeline
is known. Also, remove the warning logged when there are too many windows as it
doesn't add much.

The player's current period index was not masked while there were
unacknowledged seeks. This led to the displayed position jumping, between when
seekTo was called (after which the position would be masked but not the period
index) and the seek being acknowledged (at which point the time bar's position
would jump back to the seek position, due to the period index being resolved).
Mask the period index, like the window index, to fix this behavior.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=152116040

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

@@ -65,6 +65,7 @@
 
   // Playback information when there is a pending seek/set source operation.
   private int maskingWindowIndex;
+  private int maskingPeriodIndex;
   private long maskingWindowPositionMs;
 
   /**
@@ -187,6 +188,22 @@ public void seekTo(int windowIndex, long positionMs) {
     }
     pendingSeekAcks++;
     maskingWindowIndex = windowIndex;
+    if (timeline.isEmpty()) {
+      maskingPeriodIndex = 0;
+    } else {
+      timeline.getWindow(windowIndex, window);
+      long resolvedPositionMs =
+          positionMs == C.TIME_UNSET ? window.getDefaultPositionUs() : positionMs;
+      int periodIndex = window.firstPeriodIndex;
+      long periodPositionUs = window.getPositionInFirstPeriodUs() + C.msToUs(resolvedPositionMs);
+      long periodDurationUs = timeline.getPeriod(periodIndex, period).getDurationUs();
+      while (periodDurationUs != C.TIME_UNSET && periodPositionUs >= periodDurationUs
+          && periodIndex < window.lastPeriodIndex) {
+        periodPositionUs -= periodDurationUs;
+        periodDurationUs = timeline.getPeriod(++periodIndex, period).getDurationUs();
+      }
+      maskingPeriodIndex = periodIndex;
+    }
     if (positionMs == C.TIME_UNSET) {
       maskingWindowPositionMs = 0;
       internalPlayer.seekTo(timeline, windowIndex, C.TIME_UNSET);
@@ -235,7 +252,11 @@ public void blockingSendMessages(ExoPlayerMessage... messages) {
 
   @Override
   public int getCurrentPeriodIndex() {
-    return playbackInfo.periodIndex;
+    if (timeline.isEmpty() || pendingSeekAcks > 0) {
+      return maskingPeriodIndex;
+    } else {
+      return playbackInfo.periodIndex;
+    }
   }
 
   @Override

library/ui/src/main/java/com/google/android/exoplayer2/ui/PlaybackControlView.java

@@ -21,7 +21,6 @@
 import android.content.res.TypedArray;
 import android.os.SystemClock;
 import android.util.AttributeSet;
-import android.util.Log;
 import android.view.KeyEvent;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -34,6 +33,7 @@
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.TrackGroupArray;
 import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.util.Arrays;
 import java.util.Formatter;
@@ -345,8 +345,9 @@ public void setPlayer(ExoPlayer player) {
 
   /**
    * Sets whether the time bar should show all windows, as opposed to just the current one. If the
-   * timeline has more than {@link #MAX_WINDOWS_FOR_MULTI_WINDOW_TIME_BAR} windows the time bar will
-   * fall back to showing a single window.
+   * timeline has a period with unknown duration or more than
+   * {@link #MAX_WINDOWS_FOR_MULTI_WINDOW_TIME_BAR} windows the time bar will fall back to showing a
+   * single window.
    *
    * @param showMultiWindowTimeBar Whether the time bar should show all windows.
    */
@@ -523,14 +524,8 @@ private void updateTimeBarMode() {
     if (player == null) {
       return;
     }
-    if (showMultiWindowTimeBar) {
-      if (player.getCurrentTimeline().getWindowCount() <= MAX_WINDOWS_FOR_MULTI_WINDOW_TIME_BAR) {
-        multiWindowTimeBar = true;
-        return;
-      }
-      Log.w(TAG, "Too many windows for multi-window time bar. Falling back to showing one window.");
-    }
-    multiWindowTimeBar = false;
+    multiWindowTimeBar = showMultiWindowTimeBar
+        && canShowMultiWindowTimeBar(player.getCurrentTimeline(), period);
   }
 
   private void updateProgress() {
@@ -568,10 +563,7 @@ private void updateProgress() {
             } else {
               isInAdBreak = false;
               long periodDurationUs = period.getDurationUs();
-              if (periodDurationUs == C.TIME_UNSET) {
-                durationUs = C.TIME_UNSET;
-                break;
-              }
+              Assertions.checkState(periodDurationUs != C.TIME_UNSET);
               long periodDurationInWindowUs = periodDurationUs;
               if (j == window.firstPeriodIndex) {
                 periodDurationInWindowUs -= window.positionInFirstPeriodUs;
@@ -797,6 +789,26 @@ private static boolean isHandledMediaKey(int keyCode) {
         || keyCode == KeyEvent.KEYCODE_MEDIA_PREVIOUS;
   }
 
+  /**
+   * Returns whether the specified {@code timeline} can be shown on a multi-window time bar.
+   *
+   * @param timeline The {@link Timeline} to check.
+   * @param period A scratch {@link Timeline.Period} instance.
+   * @return Whether the specified timeline can be shown on a multi-window time bar.
+   */
+  private static boolean canShowMultiWindowTimeBar(Timeline timeline, Timeline.Period period) {
+    if (timeline.getWindowCount() > MAX_WINDOWS_FOR_MULTI_WINDOW_TIME_BAR) {
+      return false;
+    }
+    int periodCount = timeline.getPeriodCount();
+    for (int i = 0; i < periodCount; i++) {
+      if (timeline.getPeriod(i, period).durationUs == C.TIME_UNSET) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   private final class ComponentListener implements ExoPlayer.EventListener, TimeBar.OnScrubListener,
       OnClickListener {