image-burner: adding user image-burner to group disk and chronos-access.

This grants user image-burner write access to mounted disk and read
access to files in directory Downloads.

TEST=Build image with updated package
chromeos-base/chromeos-imageburner, verify that Recovery Util can burn
CrOS images to usb drives with sandboxed image-burner daemon.

Cq-Depend: chromium:2872959
Change-Id: If83bc9fb6ffbf32ea38885d53f9711c07024fe0c
Reviewed-by: Jorge Lucangeli Obes <>
Reviewed-by: Nicole Anderson-Au <>
Reviewed-by: Betul Soysal <>
Tested-by: Zi Lin <>
Commit-Queue: Zi Lin <>
diff --git a/profiles/base/accounts/group/chronos-access b/profiles/base/accounts/group/chronos-access
index 3a19b96..e3cea79 100644
--- a/profiles/base/accounts/group/chronos-access
+++ b/profiles/base/accounts/group/chronos-access
@@ -4,4 +4,4 @@
 # mostly system daemons running as a non-chronos user, group permissions
 # to access files/directories owned by chronos.
 # This includes all users accessing opencryptoki database files.
diff --git a/profiles/base/accounts/group/disk b/profiles/base/accounts/group/disk
index f425190..9ce306f 100644
--- a/profiles/base/accounts/group/disk
+++ b/profiles/base/accounts/group/disk
@@ -1,3 +1,3 @@