Merge pull request #4480 from drhill/dev-v2_mkv_forced_default_flipped

MKV Extractor flip default and forced flag values to their proper names

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java

@@ -616,10 +616,10 @@ public final class MatroskaExtractor implements Extractor {
         currentTrack.number = (int) value;
         break;
       case ID_FLAG_DEFAULT:
-        currentTrack.flagForced = value == 1;
+        currentTrack.flagDefault = value == 1;
         break;
       case ID_FLAG_FORCED:
-        currentTrack.flagDefault = value == 1;
+        currentTrack.flagForced = value == 1;
         break;
       case ID_TRACK_TYPE:
         currentTrack.type = (int) value;