Allow MediaExtractor to create FileSource

W Binder:538_2: type=1400 audit(0.0:9): avc: denied { getattr } for path="/data/media/0/Qtc88.mp4" dev="dm-0" ino=678654 scontext=u:r:mediaextractor:s0 tcontext=u:object_r:media_rw_data_file:s0 tclass=file permissive=0

W generic : type=1400 audit(0.0:9): avc: denied { read } for path="/data/media/0/Qtc88.mp4" dev="dm-0" ino=678654 scontext=u:r:mediaextractor:s0 tcontext=u:object_r:media_rw_data_file:s0 tclass=file permissive=0

Test: Photos, Play Music, Play Movies, Youtube
Bug: 29125703
Change-Id: If84ab43b934944abf4c416db751ab6694835df83

public/mediaextractor.te

@@ -20,6 +20,9 @@ allow mediaextractor proc_meminfo:file r_file_perms;
 
 crash_dump_fallback(mediaextractor)
 
+# allow mediaextractor read permissions for file sources
+allow mediaextractor media_rw_data_file:file { getattr read };
+
 ###
 ### neverallow rules
 ###