Add isandrk to OWNERS for device_local_account_util

Bug: 
Change-Id: I2325e83ced67c5388a36d38790ba6e366152bc8f
Reviewed-on: https://chromium-review.googlesource.com/793711Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Ivan Šandrk <isandrk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520608}

extensions/browser/OWNERS

@@ -15,3 +15,6 @@ per-file extension_function_histogram_value.h=asvitkine@chromium.org
 per-file extension_function_histogram_value.h=isherman@chromium.org
 per-file extension_function_histogram_value.h=jar@chromium.org
 per-file extension_function_histogram_value.h=mpearson@chromium.org
+
+# DeviceLocalAccount reviewers.
+per-file device_local_account_util*=isandrk@chromium.org