[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/cellular_service.cc b/cellular_service.cc
index bc27c5b..e2de6b7 100644
--- a/cellular_service.cc
+++ b/cellular_service.cc
@@ -57,10 +57,10 @@
   cellular_->Activate(carrier, error);
 }
 
-string CellularService::GetStorageIdentifier(const string &mac) {
+string CellularService::GetStorageIdentifier() {
   string id = base::StringPrintf("%s_%s_%s",
                                  kServiceType,
-                                 mac.c_str(),
+                                 cellular_->address().c_str(),
                                  serving_operator_.GetName().c_str());
   std::replace_if(id.begin(), id.end(), &Service::LegalChar, '_');
   return id;