[shill] Enable default profile to persist device info

Make Profile::Save() take a pointer to a vector of DeviceRefPtrs.  The base
implementation ignores this pointer, but the DefaultProfile implementation
persists all the devices to disk.

BUG=chromium-os:17254
TEST=unit
STATUS=Verified

Change-Id: I5d72bd2319edfb9ae57366cbd5c766b558ffc8a4
Reviewed-on: http://gerrit.chromium.org/gerrit/8057
Commit-Ready: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
diff --git a/default_profile.h b/default_profile.h
index 59a75c3..d362f48 100644
--- a/default_profile.h
+++ b/default_profile.h
@@ -30,6 +30,9 @@
                  const Manager::Properties &manager_props);
   virtual ~DefaultProfile();
 
+  // Persists profile information, as well as that of discovered devices
+  // and bound services, to disk.
+  // Returns true on success, false on failure.
   virtual bool Save(StoreInterface *storage);
 
   // Sets |path| to the persistent store file path for the default, global