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/mock_metrics.cc b/mock_metrics.cc
new file mode 100644
index 0000000..330fc91
--- /dev/null
+++ b/mock_metrics.cc
@@ -0,0 +1,13 @@
+// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "shill/mock_metrics.h"
+
+namespace shill {
+
+MockMetrics::MockMetrics() {}
+
+MockMetrics::~MockMetrics() {}
+
+}