Correct language propagation

Issue: #1784

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131811458

library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java

@@ -547,24 +547,24 @@ private void buildTracks(HlsExtractorWrapper extractor) {
     int trackIndex = 0;
     for (int i = 0; i < extractorTrackCount; i++) {
       MediaFormat format = extractor.getMediaFormat(i).copyWithDurationUs(durationUs);
-      String language = null;
+      String muxedLanguage = null;
       if (MimeTypes.isAudio(format.mimeType)) {
-        language = chunkSource.getMuxedAudioLanguage();
+        muxedLanguage = chunkSource.getMuxedAudioLanguage();
       } else if (MimeTypes.APPLICATION_EIA608.equals(format.mimeType)) {
-        language = chunkSource.getMuxedCaptionLanguage();
+        muxedLanguage = chunkSource.getMuxedCaptionLanguage();
       }
       if (i == primaryExtractorTrackIndex) {
         for (int j = 0; j < chunkSourceTrackCount; j++) {
           extractorTrackIndices[trackIndex] = i;
           chunkSourceTrackIndices[trackIndex] = j;
           Variant fixedTrackVariant = chunkSource.getFixedTrackVariant(j);
           trackFormats[trackIndex++] = fixedTrackVariant == null ? format.copyAsAdaptive(null)
-              : copyWithFixedTrackInfo(format, fixedTrackVariant.format, language);
+              : copyWithFixedTrackInfo(format, fixedTrackVariant.format, muxedLanguage);
         }
       } else {
         extractorTrackIndices[trackIndex] = i;
         chunkSourceTrackIndices[trackIndex] = -1;
-        trackFormats[trackIndex++] = format.copyWithLanguage(language);
+        trackFormats[trackIndex++] = format.copyWithLanguage(muxedLanguage);
       }
     }
   }
@@ -590,14 +590,14 @@ private void setTrackEnabledState(int track, boolean enabledState) {
    *
    * @param format The {@link MediaFormat} to copy.
    * @param fixedTrackFormat The {@link Format} to incorporate into the copy.
-   * @param languageOverride The language to incorporate into the copy.
+   * @param muxedLanguage The muxed language as declared by the playlist.
    * @return The copied {@link MediaFormat}.
    */
   private static MediaFormat copyWithFixedTrackInfo(MediaFormat format, Format fixedTrackFormat,
-      String languageOverride) {
+      String muxedLanguage) {
     int width = fixedTrackFormat.width == -1 ? MediaFormat.NO_VALUE : fixedTrackFormat.width;
     int height = fixedTrackFormat.height == -1 ? MediaFormat.NO_VALUE : fixedTrackFormat.height;
-    String language = languageOverride == null ? fixedTrackFormat.language : languageOverride;
+    String language = fixedTrackFormat.language == null ? muxedLanguage : fixedTrackFormat.language;
     return format.copyWithFixedTrackInfo(fixedTrackFormat.id, fixedTrackFormat.bitrate, width,
         height, language);
   }