Map AC4 mime to audio format

Change-Id: I0b7d59782a5555b09ed4759f6cc0bc75cadff8c9
diff --git a/media/libstagefright/Utils.cpp b/media/libstagefright/Utils.cpp
index c61f4b5..6457300 100644
--- a/media/libstagefright/Utils.cpp
+++ b/media/libstagefright/Utils.cpp
@@ -1576,6 +1576,7 @@
     { MEDIA_MIMETYPE_AUDIO_VORBIS,      AUDIO_FORMAT_VORBIS },
     { MEDIA_MIMETYPE_AUDIO_OPUS,        AUDIO_FORMAT_OPUS},
     { MEDIA_MIMETYPE_AUDIO_AC3,         AUDIO_FORMAT_AC3},
+    { MEDIA_MIMETYPE_AUDIO_AC4,         AUDIO_FORMAT_AC4},
     { MEDIA_MIMETYPE_AUDIO_FLAC,        AUDIO_FORMAT_FLAC},
     { 0, AUDIO_FORMAT_INVALID }
 };