Retrieve client_id from GoogleUpdateSettings when its missing from Local State.

components/metrics/client_info.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_CLIENT_INFO_H_
+#define COMPONENTS_METRICS_CLIENT_INFO_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+
+namespace metrics {
+
+// A data object used to pass data from outside the metrics component into the
+// metrics component.
+struct ClientInfo {
+ public:
+  ClientInfo();
+  ~ClientInfo();
+
+  // The metrics ID of this client: represented as a GUID string.
+  std::string client_id;
+
+  // The installation date: represented as an epoch time in seconds.
+  int64 installation_date;

[grt (UTC plus 2), 2014/07/16 22:18:29]

i'm sure this is unrelated, but new code should include stdint.h and use int64_t
as per the comment in basictypes.h

+
+  // The date on which metrics reporting was enabled: represented as an epoch
+  // time in seconds.
+  int64 reporting_enabled_date;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ClientInfo);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_CLIENT_INFO_H_