Add persist.sys.theme.

This property will be set by system_server (to indicate the currently
selected theme for device), and can be accessed by vendor init.rc.

avc:  denied  { read } for property=persist.sys.theme pid=0 uid=0 gid=0 scontext=u:r:vendor_init:s0 tcontext=u:object_r:theme_prop:s0 tclass=file

Bug: 113028175
Test: Set a vendor init trigger that waits on `persist.sys.theme`. Check
      that the trigger fires without denial.
Change-Id: Ia85b1a8dfc118efdbb9337ca017c8fb7958dc386
Merged-In: Ibb4e392d5059b76059f36f7d11ba82cd65cbe970
(cherry picked from commit 75182a1ea645d3fa1e4c3e9f77851d90ff7cc803)
diff --git a/private/compat/28.0/28.0.ignore.cil b/private/compat/28.0/28.0.ignore.cil
index 0994389..66caf4b 100644
--- a/private/compat/28.0/28.0.ignore.cil
+++ b/private/compat/28.0/28.0.ignore.cil
@@ -135,6 +135,7 @@
     task_profiles_file
     testharness_service
     test_harness_prop
+    theme_prop
     time_prop
     timedetector_service
     timezonedetector_service
diff --git a/private/property_contexts b/private/property_contexts
index 2473cdb..85111a3 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -59,6 +59,7 @@
 persist.netd.stable_secret      u:object_r:netd_stable_secret_prop:s0
 persist.sys.            u:object_r:system_prop:s0
 persist.sys.safemode    u:object_r:safemode_prop:s0
+persist.sys.theme       u:object_r:theme_prop:s0
 persist.sys.fflag.override.settings_dynamic_system    u:object_r:dynamic_system_prop:s0
 ro.sys.safemode         u:object_r:safemode_prop:s0
 persist.sys.audit_safemode      u:object_r:safemode_prop:s0
diff --git a/private/system_server.te b/private/system_server.te
index 3549353..20f2437 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -573,6 +573,7 @@
 set_prop(system_server, exported2_system_prop)
 set_prop(system_server, exported3_system_prop)
 set_prop(system_server, safemode_prop)
+set_prop(system_server, theme_prop)
 set_prop(system_server, dhcp_prop)
 set_prop(system_server, net_radio_prop)
 set_prop(system_server, net_dns_prop)