debugd: log_tool: Change group to kDebugfsGroup to obtain EC panicinfo

/sys/kernel/debug is only accessible by user in debugfs-access group,
even though the panicinfo file itself is world-readable.

BUG=chromium:527904
BUG=chromium:643031
TEST=File feedback, panicinfo is present

Change-Id: I98fff3a511b944639bab10f78db8581923c4a32e
Previous-Reviewed-on: https://chromium-review.googlesource.com/379678
(cherry picked from commit f59e261a0cfd99b36a6772dcc266b915ad3baa26)
Reviewed-on: https://chromium-review.googlesource.com/381755
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Commit-Queue: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
diff --git a/debugd/src/log_tool.cc b/debugd/src/log_tool.cc
index 9eca4b7..4df7613 100644
--- a/debugd/src/log_tool.cc
+++ b/debugd/src/log_tool.cc
@@ -66,7 +66,10 @@
   { "cros_ec",
     "/bin/cat /var/log/cros_ec.previous /var/log/cros_ec.log 2> /dev/null" },
   { "cros_ec_panicinfo",
-    "/bin/cat /sys/kernel/debug/cros_ec/panicinfo 2> /dev/null" },
+    "/bin/cat /sys/kernel/debug/cros_ec/panicinfo 2> /dev/null",
+    SandboxedProcess::kDefaultUser,
+    kDebugfsGroup
+  },
   { "dmesg", "/bin/dmesg" },
   { "ec_info", "/bin/cat /var/log/ec_info.txt" },
   { "eventlog", "/bin/cat /var/log/eventlog.txt" },