Create and integrate a metrics service client into Blimp engine.

blimp/engine/app/blimp_metrics_service_client.h

Index: blimp/engine/app/blimp_metrics_service_client.h
diff --git a/blimp/engine/app/blimp_metrics_service_client.h b/blimp/engine/app/blimp_metrics_service_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..ca374f4481eba45d7b847dfeb48edd9521567477
--- /dev/null
+++ b/blimp/engine/app/blimp_metrics_service_client.h
@@ -0,0 +1,33 @@
+// Copyright 2016 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 BLIMP_ENGINE_APP_BLIMP_METRICS_SERVICE_CLIENT_H_
+#define BLIMP_ENGINE_APP_BLIMP_METRICS_SERVICE_CLIENT_H_
+
+#include <stdint.h>
+
+#include <string>

[Wez, 2016/05/01 00:12:59]

no need for blank between stdint.h and string includes?

+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+
+class PrefService;
+
+namespace net {
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace blimp {
+namespace engine {
+
+void InitializeBlimpMetrics(

[Wez, 2016/05/01 00:12:59]

Please a add a brief comment explaining what the supplied parameters are for
e.g. "|pref_service| is used to log metrics to the chosen PrefStore." or
whatever.

+    std::unique_ptr<PrefService> pref_service,
+    scoped_refptr<net::URLRequestContextGetter> request_context_getter);
+
+void FinalizeBlimpMetrics();

[Wez, 2016/05/01 00:12:59]

nit: Consider commenting on what guarantees there are on the state of the
metrics service at the point at which this call returns - does the metrics
system shut down asynchronously or synchronously in response to the call, for
example.

+
+}  // namespace engine
+}  // namespace blimp
+
+#endif  // BLIMP_ENGINE_APP_BLIMP_METRICS_SERVICE_CLIENT_H_