Fix buffering issue for live streams

Issue: #1825

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133401980

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

@@ -243,16 +243,8 @@ import java.util.concurrent.CopyOnWriteArraySet;
     if (timeline == null || pendingSeekAcks > 0) {
       return maskingWindowPositionMs;
     } else {
-      int periodIndex = playbackInfo.periodIndex;
-      timeline.getPeriod(periodIndex, period);
-      int windowIndex = period.windowIndex;
-      timeline.getWindow(windowIndex, window);
-      if (window.firstPeriodIndex == periodIndex && window.lastPeriodIndex == periodIndex
-          && window.getPositionInFirstPeriodUs() == 0
-          && window.getDurationUs() == period.getDurationUs()) {
-        return C.usToMs(playbackInfo.bufferedPositionUs);
-      }
-      return getCurrentPosition();
+      timeline.getPeriod(playbackInfo.periodIndex, period);
+      return period.getPositionInWindowMs() + C.usToMs(playbackInfo.bufferedPositionUs);
     }
   }
 

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

@@ -1071,7 +1071,7 @@ import java.io.IOException;
     long nextLoadPositionUs = loadingPeriodHolder.mediaPeriod.getNextLoadPositionUs();
     if (nextLoadPositionUs != C.TIME_END_OF_SOURCE) {
       long loadingPeriodPositionUs = rendererPositionUs
-          - loadingPeriodHolder.rendererPositionOffsetUs + loadingPeriodHolder.startPositionUs;
+          - loadingPeriodHolder.rendererPositionOffsetUs;
       long bufferedDurationUs = nextLoadPositionUs - loadingPeriodPositionUs;
       boolean continueLoading = loadControl.shouldContinueLoading(bufferedDurationUs);
       setIsLoading(continueLoading);