shill: On Service::Connect, connect the modem device to the network.

Also, uncouple the DBusProperties signal callbacks from Modem to make the proxy
implementation more consistent with the other proxies.

BUG=chromium-os:18727
TEST=unit tests

Change-Id: Icdddea8d2a30803150f2a159fdc5a719e960f95d
Reviewed-on: http://gerrit.chromium.org/gerrit/5444
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Chris Masone <cmasone@chromium.org>
diff --git a/cellular_service.cc b/cellular_service.cc
index 3685ccd..cbe9e02 100644
--- a/cellular_service.cc
+++ b/cellular_service.cc
@@ -10,15 +10,11 @@
 #include <chromeos/dbus/service_constants.h>
 
 #include "shill/cellular.h"
-#include "shill/control_interface.h"
-#include "shill/device.h"
-#include "shill/device_info.h"
-#include "shill/manager.h"
-#include "shill/shill_event.h"
 
 using std::string;
 
 namespace shill {
+
 CellularService::CellularService(ControlInterface *control_interface,
                                  EventDispatcher *dispatcher,
                                  Manager *manager,
@@ -48,7 +44,9 @@
 
 CellularService::~CellularService() { }
 
-void CellularService::Connect() { }
+void CellularService::Connect() {
+  cellular_->Connect();
+}
 
 void CellularService::Disconnect() { }