[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/ethernet_service.cc b/ethernet_service.cc
index 8db66cb..ee02f6d 100644
--- a/ethernet_service.cc
+++ b/ethernet_service.cc
@@ -52,8 +52,9 @@
   return ethernet_->GetRpcIdentifier();
 }
 
-string EthernetService::GetStorageIdentifier(const string &mac) {
-  return base::StringPrintf("%s_%s", kServiceType, mac.c_str());
+string EthernetService::GetStorageIdentifier() {
+  return base::StringPrintf("%s_%s",
+                            kServiceType, ethernet_->address().c_str());
 }
 
 }  // namespace shill