Add chronos to arc-camera group.

This is needed for Chrome browser process to access the unix domain
socket /var/run/camera/camera3.sock to talk to the camera HAL.

BUG=b:36233258, b:32690003
CQ-DEPEND=CL:546796
TEST=Make sure Chrome starts and Mojo connection to the camera HAL
     is started successfully.

Change-Id: Id7143465a7e7849fa36234e7b6c6045bdc2c83e8
Reviewed-on: https://chromium-review.googlesource.com/505827
Reviewed-by: Ricky Liang <jcliang@chromium.org>
Tested-by: Ricky Liang <jcliang@chromium.org>
Commit-Queue: Ricky Liang <jcliang@chromium.org>
diff --git a/profiles/base/accounts/group/arc-camera b/profiles/base/accounts/group/arc-camera
index 6f529a6..e140fbf 100644
--- a/profiles/base/accounts/group/arc-camera
+++ b/profiles/base/accounts/group/arc-camera
@@ -1,3 +1,3 @@
 group:arc-camera
 gid:603
-users:
+users:chronos