SmoothStreaming: Test for fourCC equal to DFXP

Issue: #4824

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213285790

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/manifest/SsManifestParser.java

@@ -715,7 +715,7 @@ public class SsManifestParser implements ParsingLoadable.Parser<SsManifest> {
       } else if (fourCC.equalsIgnoreCase("AAC") || fourCC.equalsIgnoreCase("AACL")
       } else if (fourCC.equalsIgnoreCase("AAC") || fourCC.equalsIgnoreCase("AACL")
           || fourCC.equalsIgnoreCase("AACH") || fourCC.equalsIgnoreCase("AACP")) {
           || fourCC.equalsIgnoreCase("AACH") || fourCC.equalsIgnoreCase("AACP")) {
         return MimeTypes.AUDIO_AAC;
         return MimeTypes.AUDIO_AAC;
-      } else if (fourCC.equalsIgnoreCase("TTML")) {
+      } else if (fourCC.equalsIgnoreCase("TTML") || fourCC.equalsIgnoreCase("DFXP")) {
         return MimeTypes.APPLICATION_TTML;
         return MimeTypes.APPLICATION_TTML;
       } else if (fourCC.equalsIgnoreCase("ac-3") || fourCC.equalsIgnoreCase("dac3")) {
       } else if (fourCC.equalsIgnoreCase("ac-3") || fourCC.equalsIgnoreCase("dac3")) {
         return MimeTypes.AUDIO_AC3;
         return MimeTypes.AUDIO_AC3;