shill: Connect Ethernet Device to DHCPConfig.

Most of the implementation is in the base Device class.

BUG=chromium-os:16794
TEST=unit test

Change-Id: I583761f7e54c88b043ce4343cb43f8298aaedf8b
Reviewed-on: http://gerrit.chromium.org/gerrit/2949
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/dhcp_provider.h b/dhcp_provider.h
index a0f3914..add55b1 100644
--- a/dhcp_provider.h
+++ b/dhcp_provider.h
@@ -55,6 +55,8 @@
  private:
   friend struct DefaultSingletonTraits<DHCPProvider>;
   friend class DHCPProviderTest;
+  friend class DeviceInfoTest;
+  friend class DeviceTest;
   FRIEND_TEST(DHCPProviderTest, CreateConfig);
 
   typedef std::map<int, DHCPConfigRefPtr> PIDConfigMap;
@@ -64,7 +66,7 @@
   virtual ~DHCPProvider();
 
   // A single listener is used to catch signals from all DHCP clients and
-  // dispatch them to the appropriate proxy.
+  // dispatch them to the appropriate DHCP configuration instance.
   scoped_ptr<DHCPListenerInterface> listener_;
 
   // A map that binds PIDs to DHCP configuration instances.