Add UID and directory for RELRO sharing support.

Define a UID to be used by the process responsible for creating shared
RELRO files for the WebView native library, and create a directory owned
by that UID to use to store the files.

Bug: 13005501
Change-Id: I5bbb1e1035405e5534b2681f554fe16f74e3da1a
diff --git a/rootdir/init.rc b/rootdir/init.rc
index ed756e0..2ea3cd6 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -227,6 +227,7 @@
     mkdir /data/misc/sms 0770 system radio
     mkdir /data/misc/zoneinfo 0775 system system
     mkdir /data/misc/vpn 0770 system vpn
+    mkdir /data/misc/shared_relro 0771 shared_relro shared_relro
     mkdir /data/misc/systemkeys 0700 system system
     mkdir /data/misc/wifi 0770 wifi wifi
     mkdir /data/misc/wifi/sockets 0770 wifi wifi