Transcoding: Add file read/write permission to service.

This is needed for the transcoding service to read from the
source fd and write to destination fd.

Bug: 145628554
Test: atest MediaTranscodeManagerTest
Change-Id: Icffed1e402bc2fb593e925de0742c0d7552b50bc
diff --git a/public/mediatranscoding.te b/public/mediatranscoding.te
index 85c4a6c..2e539df 100644
--- a/public/mediatranscoding.te
+++ b/public/mediatranscoding.te
@@ -12,6 +12,11 @@
 allow mediatranscoding activity_service:service_manager find;
 allow mediatranscoding untrusted_app:binder call;
 
+# allow mediatranscoding service read/write permissions for file sources
+allow mediatranscoding sdcardfs:file { getattr read write };
+allow mediatranscoding media_rw_data_file:file { getattr read write };
+allow mediatranscoding apk_data_file:file { getattr read };
+
 # mediatranscoding should never execute any executable without a
 # domain transition
 neverallow mediatranscoding { file_type fs_type }:file execute_no_trans;