Add /data/misc/a11ytrace folder to store accessibility trace files.

Bug: 157601519
Test: adb shell cmd accessibility start-trace
      adb shell cmd accessibility stop-trace
Change-Id: Id4224cee800fe3e10f33794c96048366a0bf09bb
diff --git a/private/system_server.te b/private/system_server.te
index a11e951..2c0eac9 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -930,6 +930,10 @@
   # Allow writing and removing window traces in /data/misc/wmtrace.
   allow system_server wm_trace_data_file:dir rw_dir_perms;
   allow system_server wm_trace_data_file:file { getattr setattr create unlink w_file_perms };
+
+  # Allow writing and removing accessibility traces in /data/misc/a11ytrace.
+  allow system_server accessibility_trace_data_file:dir rw_dir_perms;
+  allow system_server accessibility_trace_data_file:file { getattr setattr create unlink w_file_perms };
 ')
 
 # For AppFuse.