[shill] Start replacing bare pointers with scoped_refptrs where appropriate

BUG=chromium-os:16259
TEST=unit tests

Change-Id: I5e1531b726bbb40917d25dc3ae44da9a6a420e00
Reviewed-on: http://gerrit.chromium.org/gerrit/2236
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
diff --git a/dhcp_provider.cc b/dhcp_provider.cc
index 35f9ca1..e082d5e 100644
--- a/dhcp_provider.cc
+++ b/dhcp_provider.cc
@@ -27,7 +27,7 @@
   listener_.reset(new DHCPCDListener(this, connection));
 }
 
-DHCPConfigRefPtr DHCPProvider::CreateConfig(const Device &device) {
+DHCPConfigRefPtr DHCPProvider::CreateConfig(DeviceConstRefPtr device) {
   VLOG(2) << __func__;
   return DHCPConfigRefPtr(new DHCPConfig(this, device));
 }