Add a mechanism for collecting Rappor samples on a daily interval.

components/metrics/daily_observer.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_DAILY_OBSERVER_H_
+#define COMPONENTS_METRICS_DAILY_OBSERVER_H_
+
+#include "base/macros.h"
+
+namespace metrics {
+
+// DailyObserver receives notifications from RapporService.
+// An observer must be added, removed, and notified on the same thread.
+class DailyObserver {
+public:

[Alexei Svitkine (slow), 2014/09/05 20:00:33]

Nit: Indent 1 more, same below.

[Steven Holte, 2014/09/05 21:15:07]

Done.

+  // Called when daily metrics should be collected.
+  virtual void OnDailyInterval() = 0;
+
+protected:
+  DailyObserver();
+  virtual ~DailyObserver();
+
+private:
+  DISALLOW_COPY_AND_ASSIGN(DailyObserver);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_DAILY_OBSERVER_H_