Specify locale when using String.format.

library/src/main/java/com/google/android/exoplayer/extractor/webm/WebmExtractor.java

@@ -43,6 +43,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * An extractor to facilitate data retrieval from the WebM container format.
@@ -912,8 +913,8 @@ public final class WebmExtractor implements Extractor {
       int seconds = (int) (timeUs / 1000000);
       timeUs -= (seconds * 1000000);
       int milliseconds = (int) (timeUs / 1000);
-      timeCodeData = String.format("%02d:%02d:%02d,%03d", hours, minutes, seconds, milliseconds)
-          .getBytes();
+      timeCodeData = String.format(Locale.US, "%02d:%02d:%02d,%03d",
+          hours, minutes, seconds, milliseconds).getBytes();
     }
     System.arraycopy(timeCodeData, 0, subripSampleData, SUBRIP_PREFIX_END_TIMECODE_OFFSET,
         SUBRIP_TIMECODE_LENGTH);