Move the MP3 code to it's own directory

dom/media/moz.build

@@ -30,6 +30,7 @@ DIRS += [
     'ipc',
     'mediasink',
     'mediasource',
+    'mp3',
     'ogg',
     'platforms',
     'systemservices',
@@ -125,8 +126,6 @@ EXPORTS += [
     'MediaTimer.h',
     'MediaTrack.h',
     'MediaTrackList.h',
-    'MP3Decoder.h',
-    'MP3Demuxer.h',
     'NextFrameSeekTask.h',
     'nsIDocumentActivity.h',
     'PrincipalChangeObserver.h',
@@ -233,8 +232,6 @@ UNIFIED_SOURCES += [
     'MediaTimer.cpp',
     'MediaTrack.cpp',
     'MediaTrackList.cpp',
-    'MP3Decoder.cpp',
-    'MP3Demuxer.cpp',
     'NextFrameSeekTask.cpp',
     'QueueObject.cpp',
     'SeekJob.cpp',