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/modem.cc b/modem.cc
index 87e3d3e..8e15156 100644
--- a/modem.cc
+++ b/modem.cc
@@ -13,6 +13,7 @@
 #include "shill/rtnl_handler.h"
 
 using std::string;
+using std::vector;
 
 namespace shill {
 
@@ -122,4 +123,18 @@
   }
 }
 
+void Modem::OnDBusPropertiesChanged(
+    const string &interface,
+    const DBusPropertiesMap &changed_properties,
+    const vector<string> &invalidated_properties) {
+  // Ignored.
+}
+
+void Modem::OnModemManagerPropertiesChanged(
+    const string &interface,
+    const DBusPropertiesMap &properties) {
+  // TODO(petkov): Implement this.
+  NOTIMPLEMENTED();
+}
+
 }  // namespace shill