Allow only system_server to read uid_time_in_state

Bug: 62706738
Bug: 34133340
Test: Check that uid_time_in_state can't be read from
the shell without root permissions and that
"dumpsys batterystats --checkin| grep ctf" shows frequency
data (system_server was able to read uid_time_in_state)

Change-Id: Ic6a54da4ebcc9e10b0e3af8f14a45d7408e8686e
diff --git a/private/system_server.te b/private/system_server.te
index 2bfd4cd..243ad23 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -130,6 +130,9 @@
 # Write /proc/uid_procstat/set.
 allow system_server proc_uid_procstat_set:file { w_file_perms getattr };
 
+# Read /proc/uid_time_in_state.
+allow system_server proc_uid_time_in_state:file r_file_perms;
+
 # Write to /proc/sysrq-trigger.
 allow system_server proc_sysrq:file rw_file_perms;