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/modem_info.h b/modem_info.h
index 4ecc9f4..3a5c6fd 100644
--- a/modem_info.h
+++ b/modem_info.h
@@ -18,6 +18,7 @@
 class EventDispatcher;
 class GLib;
 class Manager;
+class Metrics;
 class ModemManager;
 
 // Manages modem managers.
@@ -25,6 +26,7 @@
  public:
   ModemInfo(ControlInterface *control_interface,
             EventDispatcher *dispatcher,
+            Metrics *metrics,
             Manager *manager,
             GLib *glib);
   ~ModemInfo();
@@ -53,6 +55,7 @@
 
   ControlInterface *control_interface_;
   EventDispatcher *dispatcher_;
+  Metrics *metrics_;
   Manager *manager_;
   GLib *glib_;