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..e3bcfa492a508b351c6f067762d616d4b6fcd2a6
--- /dev/null
+++ b/blimp/engine/app/blimp_metrics_service_client.h
@@ -0,0 +1,41 @@
+// 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>
+
+#include "base/macros.h"
+
+class PrefService;
+
+namespace metrics {
+struct ClientInfo;
+class MetricsStateManager;
+}  // namespace metrics
+
+namespace net {
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace blimp {
+namespace engine {
+class BlimpMetricsServiceClient;
+
+// Provides a pointer to a LazyInstance<BlimpMetricsServiceClient>::Leaky.
+BlimpMetricsServiceClient* GetBlimpMetricsServiceClientInstance();
+
+void InitializeBlimpMetricsServiceClient(

[Wez, 2016/04/27 22:30:27]

Suggest InitializeBlimpMetrics - sufficiently unambiguous but this function also
initializes the whole metrics stack. :)

We can add an InitializeBlimpMetricsForTest() function that accepts additional
test-only parameters if necessary, if mocking the PrefService and/or
URLRequestContextGetter are insufficient.

[Jess, 2016/04/29 22:20:13]

Done.

+    PrefService* pref_service,
+    net::URLRequestContextGetter* request_context_getter);
+
+void FinalizeBlimpMetricsServiceClient();
+
+}  // namespace engine
+}  // namespace blimp
+
+#endif  // BLIMP_ENGINE_APP_BLIMP_METRICS_SERVICE_CLIENT_H_