Simplify some buffered position related code.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=215704344

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

@@ -496,10 +496,8 @@ import java.util.Collections;
 
     // Update the buffered position and total buffered duration.
     MediaPeriodHolder loadingPeriod = queue.getLoadingPeriod();
-    playbackInfo.bufferedPositionUs =
-        loadingPeriod.getBufferedPositionUs(/* convertEosToDuration= */ true);
-    playbackInfo.totalBufferedDurationUs =
-        playbackInfo.bufferedPositionUs - loadingPeriod.toPeriodTime(rendererPositionUs);
+    playbackInfo.bufferedPositionUs = loadingPeriod.getBufferedPositionUs();
+    playbackInfo.totalBufferedDurationUs = getTotalBufferedDurationUs();
   }
 
   private void doSomeWork() throws ExoPlaybackException, IOException {
@@ -1097,12 +1095,10 @@ import java.util.Collections;
     }
     // Renderers are ready and we're loading. Ask the LoadControl whether to transition.
     MediaPeriodHolder loadingHolder = queue.getLoadingPeriod();
-    long bufferedPositionUs = loadingHolder.getBufferedPositionUs(!loadingHolder.info.isFinal);
-    return bufferedPositionUs == C.TIME_END_OF_SOURCE
+    boolean bufferedToEnd = loadingHolder.isFullyBuffered() && loadingHolder.info.isFinal;
+    return bufferedToEnd
         || loadControl.shouldStartPlayback(
-            bufferedPositionUs - loadingHolder.toPeriodTime(rendererPositionUs),
-            mediaClock.getPlaybackParameters().speed,
-            rebuffering);
+            getTotalBufferedDurationUs(), mediaClock.getPlaybackParameters().speed, rebuffering);
   }
 
   private boolean isTimelineReady() {
@@ -1574,7 +1570,7 @@ import java.util.Collections;
       return;
     }
     long bufferedDurationUs =
-        nextLoadPositionUs - loadingPeriodHolder.toPeriodTime(rendererPositionUs);
+        getTotalBufferedDurationUs(/* bufferedPositionInLoadingPeriodUs= */ nextLoadPositionUs);
     boolean continueLoading =
         loadControl.shouldContinueLoading(
             bufferedDurationUs, mediaClock.getPlaybackParameters().speed);
@@ -1680,6 +1676,17 @@ import java.util.Collections;
     }
   }
 
+  private long getTotalBufferedDurationUs() {
+    return getTotalBufferedDurationUs(playbackInfo.bufferedPositionUs);
+  }
+
+  private long getTotalBufferedDurationUs(long bufferedPositionInLoadingPeriodUs) {
+    MediaPeriodHolder loadingPeriodHolder = queue.getLoadingPeriod();
+    return loadingPeriodHolder == null
+        ? 0
+        : bufferedPositionInLoadingPeriodUs - loadingPeriodHolder.toPeriodTime(rendererPositionUs);
+  }
+
   private void updateLoadControlTrackSelection(
       TrackGroupArray trackGroups, TrackSelectorResult trackSelectorResult) {
     loadControl.onTracksSelected(renderers, trackGroups, trackSelectorResult.selections);

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

@@ -133,23 +133,18 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
   }
 
   /**
-   * Returns the buffered position in microseconds. If the period is buffered to the end then
-   * {@link C#TIME_END_OF_SOURCE} is returned unless {@code convertEosToDuration} is true, in which
-   * case the period duration is returned.
+   * Returns the buffered position in microseconds. If the period is buffered to the end, then the
+   * period duration is returned.
    *
-   * @param convertEosToDuration Whether to return the period duration rather than
-   *     {@link C#TIME_END_OF_SOURCE} if the period is fully buffered.
    * @return The buffered position in microseconds.
    */
-  public long getBufferedPositionUs(boolean convertEosToDuration) {
+  public long getBufferedPositionUs() {
     if (!prepared) {
       return info.startPositionUs;
     }
     long bufferedPositionUs =
         hasEnabledTracks ? mediaPeriod.getBufferedPositionUs() : C.TIME_END_OF_SOURCE;
-    return bufferedPositionUs == C.TIME_END_OF_SOURCE && convertEosToDuration
-        ? info.durationUs
-        : bufferedPositionUs;
+    return bufferedPositionUs == C.TIME_END_OF_SOURCE ? info.durationUs : bufferedPositionUs;
   }
 
   /**