Pass MetricsServiceClient into MetricsService, and create a simple stubbed TestMetricsServiceClient…

components/metrics/test_metrics_service_client.h

+// Copyright 2014 The Chromium 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 COMPONENTS_METRICS_TEST_METRICS_SERVICE_CLIENT_H_
+#define COMPONENTS_METRICS_TEST_METRICS_SERVICE_CLIENT_H_
+
+#include "components/metrics/metrics_service_client.h"
+
+namespace metrics {
+
+// A simple concrete implementation of the MetricsServiceClient interface, for
+// use in tests.
+class TestMetricsServiceClient : public MetricsServiceClient {
+ public:
+  TestMetricsServiceClient();
+  virtual ~TestMetricsServiceClient();
+
+  // MetricsServiceClient:
+  virtual void SetClientID(const std::string& client_id) OVERRIDE;
+  virtual bool IsOffTheRecordSessionActive() OVERRIDE;
+  virtual std::string GetApplicationLocale() OVERRIDE;
+  virtual bool GetBrand(std::string* brand_code) OVERRIDE;
+  virtual SystemProfileProto::Channel GetChannel() OVERRIDE;
+  virtual std::string GetVersionString() OVERRIDE;
+
+  const std::string& get_client_id() const { return client_id_; }
+
+ private:
+  std::string client_id_;
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_TEST_METRICS_SERVICE_CLIENT_H_