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/wifi_endpoint_unittest.cc b/wifi_endpoint_unittest.cc
index 556b966..a81dff4 100644
--- a/wifi_endpoint_unittest.cc
+++ b/wifi_endpoint_unittest.cc
@@ -93,7 +93,8 @@
                                  const WiFiRefPtr &wifi,
                                  const std::string &ssid,
                                  const std::string &bssid) {
-    return WiFiEndpoint::MakeOpenEndpoint(proxy_factory, wifi, ssid, bssid);
+    return WiFiEndpoint::MakeOpenEndpoint(
+        proxy_factory, wifi, ssid, bssid, 0, 0);
   }
 
   scoped_refptr<MockWiFi> wifi() { return wifi_; }