Add OWNERS file to chromeos/disks set to ui/file_manager/OWNERS

Change-Id: Ic29cfd608d962feae46400f4ab35c8f6f9e16e7e
Reviewed-on: https://chromium-review.googlesource.com/1164150Reviewed-by: Satoru Takabayashi <satorux@google.com>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Satoru Takabayashi <satorux@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581100}

chromeos/disks/OWNERS

+file://ui/file_manager/OWNERS