Fix VOD to live transitions.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130755346

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

@@ -1051,7 +1051,7 @@ import java.io.IOException;
   private void maybeContinueLoading() {
     long nextLoadPositionUs = loadingPeriod.mediaPeriod.getNextLoadPositionUs();
     if (nextLoadPositionUs != C.END_OF_SOURCE_US) {
-      long positionUs = internalPositionUs - loadingPeriod.offsetUs;
+      long positionUs = internalPositionUs - loadingPeriod.offsetUs + loadingPeriod.startPositionUs;
       long bufferedDurationUs = nextLoadPositionUs - positionUs;
       boolean continueLoading = loadControl.shouldContinueLoading(bufferedDurationUs);
       setIsLoading(continueLoading);

library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -226,7 +226,7 @@ public final class ConcatenatingMediaSource implements MediaSource {
     @Override
     public long getWindowOffsetInFirstPeriodUs(int windowIndex) {
       int sourceIndex = getSourceIndexForWindow(windowIndex);
-      int firstWindowIndexInSource = getFirstPeriodIndexInSource(sourceIndex);
+      int firstWindowIndexInSource = getFirstWindowIndexInSource(sourceIndex);
       return timelines[sourceIndex].getWindowOffsetInFirstPeriodUs(
           windowIndex - firstWindowIndexInSource);
     }