Fix PTS wraparound in HLS+Webvtt

Issue:#2928

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=169246424

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/WebvttExtractor.java

@@ -141,8 +141,7 @@ import java.util.regex.Pattern;
           throw new ParserException("X-TIMESTAMP-MAP doesn't contain media timestamp: " + line);
         }
         vttTimestampUs = WebvttParserUtil.parseTimestampUs(localTimestampMatcher.group(1));
-        tsTimestampUs = TimestampAdjuster.ptsToUs(
-            Long.parseLong(mediaTimestampMatcher.group(1)));
+        tsTimestampUs = TimestampAdjuster.ptsToUs(Long.parseLong(mediaTimestampMatcher.group(1)));
       }
     }
 
@@ -155,8 +154,8 @@ import java.util.regex.Pattern;
     }
 
     long firstCueTimeUs = WebvttParserUtil.parseTimestampUs(cueHeaderMatcher.group(1));
-    long sampleTimeUs = timestampAdjuster.adjustSampleTimestamp(
-        firstCueTimeUs + tsTimestampUs - vttTimestampUs);
+    long sampleTimeUs = timestampAdjuster.adjustTsTimestamp(
+        TimestampAdjuster.usToPts(firstCueTimeUs + tsTimestampUs - vttTimestampUs));
     long subsampleOffsetUs = sampleTimeUs - firstCueTimeUs;
     // Output the track.
     TrackOutput trackOutput = buildTrackOutput(subsampleOffsetUs);