shill: update service signal strength and frequency from endpoints

In addition to updating the values in WiFiService, we emit
notification of the changes over RPC.

BUG=chromium-os:16786,chromium-os:16788
TEST=new unit tests, manual

Manual test: run on device, see signal strength indicator in UI
instead of "X".

Change-Id: I1ab5f064953a412387362d50e47602ee62dbe0cc
Reviewed-on: https://gerrit.chromium.org/gerrit/16000
Reviewed-by: Gary Morain <gmorain@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/service_dbus_adaptor.cc b/service_dbus_adaptor.cc
index ccdb85e..3597beb 100644
--- a/service_dbus_adaptor.cc
+++ b/service_dbus_adaptor.cc
@@ -40,6 +40,10 @@
   PropertyChanged(name, DBusAdaptor::ByteToVariant(value));
 }
 
+void ServiceDBusAdaptor::EmitUint16Changed(const string &name, uint16 value) {
+  PropertyChanged(name, DBusAdaptor::Uint16ToVariant(value));
+}
+
 void ServiceDBusAdaptor::EmitUintChanged(const string &name, uint32 value) {
   PropertyChanged(name, DBusAdaptor::Uint32ToVariant(value));
 }