[shill] Add code for persisting profiles and services to disk.

BUG=chromium-os:17253
TEST=unit

Change-Id: Ic6dbbcb10543da3f4615cb305a77f6b9b301e8bc
Reviewed-on: http://gerrit.chromium.org/gerrit/7633
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
diff --git a/device.h b/device.h
index ed7c413..995517d 100644
--- a/device.h
+++ b/device.h
@@ -76,6 +76,7 @@
   std::string GetRpcIdentifier();
   std::string GetStorageIdentifier();
 
+  const std::string &address() const { return hardware_address_; }
   const std::string &link_name() const { return link_name_; }
   int interface_index() const { return interface_index_; }
   const ConnectionRefPtr &connection() const { return connection_; }