CEA608 - Add space when handling mid-row codes

Issue: #3906

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=200526335

RELEASENOTES.md

@@ -12,8 +12,10 @@
   changes ([#4276](https://github.com/google/ExoPlayer/issues/4276)).
 * Fix `MediaCodec.native_setSurface` crash on Moto C
   ([#4315](https://github.com/google/ExoPlayer/issues/4315)).
+* Fix missing whitespace in CEA-608
+  ([#3906](https://github.com/google/ExoPlayer/issues/3906)).
 * Set `METADATA_KEY_TITLE` on media descriptions
-  ((#4292)[https://github.com/google/ExoPlayer/issues/4292]).
+  ([#4292](https://github.com/google/ExoPlayer/issues/4292)).
 * Allow apps to register custom MIME types
   ([#4264](https://github.com/google/ExoPlayer/issues/4264)).
 

library/core/src/main/java/com/google/android/exoplayer2/text/cea/Cea608Decoder.java

@@ -374,6 +374,9 @@ private boolean handleCtrl(byte cc1, byte cc2) {
   private void handleMidrowCtrl(byte cc2) {
     // TODO: support the extended styles (i.e. backgrounds and transparencies)
 
+    // A midrow control code advances the cursor.
+    currentCueBuilder.append(' ');
+
     // cc2 - 0|0|1|0|ATRBT|U
     // ATRBT is the 3-byte encoded attribute, and U is the underline toggle
     boolean isUnderlined = (cc2 & 0x01) == 0x01;