dbus::FileDescriptor has an awkward API which requires all users to call dbus::FileDescriptor::CheckValidity() on an IO-allowed thread.
As stated in https://codereview.chromium.org/9700072#msg5, IIUC this check is not needed as renderer processes don't use D-Bus at all.
We should remove dbus::FileDescriptor by replacing it with base::ScopedFD.
Comment 1 by hashimoto@chromium.org
, Jun 21 2016