Introduce MetricsServiceClient and ChromeMetricsServiceClient.

components/metrics/metrics_service_client.h

Index: components/metrics/metrics_service_client.h
===================================================================
--- components/metrics/metrics_service_client.h	(revision 0)
+++ components/metrics/metrics_service_client.h	(working copy)
@@ -0,0 +1,35 @@
+// 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_METRICS_SERVICE_CLIENT_H_
+#define COMPONENTS_METRICS_METRICS_SERVICE_CLIENT_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "components/metrics/proto/system_profile.pb.h"
+
+namespace metrics {
+
+// An abstraction of operations that depend on the embedders (e.g. Chrome)

[blundell, 2014/05/19 10:00:23]

nit: s/embedders/embedder's

[Alexei Svitkine (slow), 2014/05/19 10:55:23]

Done.

+// environment.
+class MetricsServiceClient {
+ public:
+  MetricsServiceClient();

[blundell, 2014/05/19 10:00:23]

Does this need a defined constructor and .cc file vs. just having the inlined
destructor definition?

[Alexei Svitkine (slow), 2014/05/19 10:55:23]

I know that inline ctors and dtors are generally discouraged, but maybe because
this is an interface that rule is relaxed? If we don't define the ctor we also
can't have the DISALLOW_() macro as well, but maybe that's fine.

I don't care either way. Ilya, any preference?

[Ilya Sherman, 2014/05/19 11:06:24]

No preference.  I think technically inlined constructors and destructors are
allowed as long as the class has only (a small number of) POD members (or none
at all, as in this case).

[Alexei Svitkine (slow), 2014/05/19 11:34:57]

Okay, in that case - I'll just keep the header file to keep things simpler.

Done.

+  virtual ~MetricsServiceClient();
+
+  virtual void SetClientID(const std::string& client_id) = 0;
+  virtual bool IsOffTheRecordSessionActive() = 0;
+  virtual std::string GetApplicationLocale() = 0;
+  virtual bool GetBrand(std::string* brand_code) = 0;
+  virtual SystemProfileProto::Channel GetChannel() = 0;
+  virtual std::string GetVersionString() = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MetricsServiceClient);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_METRICS_SERVICE_CLIENT_H_