Start transition the metrics library to non-static API. Use gmock in tests.

src/platform/metrics/metrics_library_mock.h

+// Copyright (c) 2010 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.
+
+#ifndef METRICS_LIBRARY_MOCK_H_
+#define METRICS_LIBRARY_MOCK_H_
+
+#include <string>
+
+#include "metrics_library.h"
+
+#include <gmock/gmock.h>
+
+class MetricsLibraryMock : public MetricsLibraryInterface {
+ public:
+  MOCK_METHOD0(Init, void());
+  MOCK_METHOD5(SendToUMA, bool(const std::string& name, int sample,
+                               int min, int max, int nbuckets));
+  MOCK_METHOD3(SendEnumToUMA, bool(const std::string& name, int sample,
+                                   int max));
+};
+
+#endif /* METRICS_LIBRARY_MOCK_H_ */