shill: Move Metrics from singleton to Shill daemon

While implementing chromium-os:24810, it was discovered that Metrics is
cleaner if it is passed around like ControlInterface, Dispatcher,
Manager, etc.  This approach also makes Metrics more testable.

BUG=chromium-os:24810
TEST=Unit tests, network_WiFiManager suite

Change-Id: I556a1bd11f21f0b93ecfeaae8855dfb99ed5e5f9
Reviewed-on: https://gerrit.chromium.org/gerrit/14099
Commit-Ready: Thieu Le <thieule@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
diff --git a/cellular_service.cc b/cellular_service.cc
index 2f6deb6..c79329a 100644
--- a/cellular_service.cc
+++ b/cellular_service.cc
@@ -22,9 +22,11 @@
 
 CellularService::CellularService(ControlInterface *control_interface,
                                  EventDispatcher *dispatcher,
+                                 Metrics *metrics,
                                  Manager *manager,
                                  const CellularRefPtr &device)
-    : Service(control_interface, dispatcher, manager, Technology::kCellular),
+    : Service(control_interface, dispatcher, metrics, manager,
+              Technology::kCellular),
       cellular_(device) {
   PropertyStore *store = this->mutable_store();
   store->RegisterConstString(flimflam::kActivationStateProperty,