Allow read access to /proc entries for other UIDs

Allow dumpstate (aka adb bugreport), servicemanager, and
surfaceflinger to access /proc entries associated with other UIDs.

Bug: 23310674
Change-Id: I385dcf0db3376ba979409cbe6fe1a468d36237ef
diff --git a/services/surfaceflinger/surfaceflinger.rc b/services/surfaceflinger/surfaceflinger.rc
index 59a43e2..eb9bd25 100644
--- a/services/surfaceflinger/surfaceflinger.rc
+++ b/services/surfaceflinger/surfaceflinger.rc
@@ -1,6 +1,6 @@
 service surfaceflinger /system/bin/surfaceflinger
     class core
     user system
-    group graphics drmrpc
+    group graphics drmrpc readproc
     onrestart restart zygote
     writepid /dev/cpuset/system-background/tasks