Reporting: Implement garbage collector.

net/reporting/reporting_garbage_collector.h

+// Copyright 2017 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 NET_REPORTING_REPORTING_GARBAGE_COLLECTOR_H_
+#define NET_REPORTING_REPORTING_GARBAGE_COLLECTOR_H_
+
+#include <memory>
+
+#include "net/base/net_export.h"
+
+namespace net {
+
+class ReportingContext;
+
+// Removes reports that have remained undelivered for too long or that have been
+// included in too many failed delivery attempts.
+class NET_EXPORT ReportingGarbageCollector {
+ public:
+  static std::unique_ptr<ReportingGarbageCollector> Create(
+      ReportingContext* context);
+
+  virtual ~ReportingGarbageCollector();
+};
+
+}  // namespace net
+
+#endif  // NET_REPORTING_REPORTING_GARBAGE_COLLECTOR_H_