[Offline Pages] Create a event/activity logger

components/offline_pages/offline_event_logger.h

+// 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 COMPONENTS_OFFLINE_PAGES_OFFLINE_EVENT_LOGGER_H_
+#define COMPONENTS_OFFLINE_PAGES_OFFLINE_EVENT_LOGGER_H_
+
+#include <deque>
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+
+namespace offline_pages {
+
+// Maximum number of recorded Logs to keep track of at any moment.
+static const size_t kMaxLogCount = 50;
+
+// Facilitates the logging of events. Subclasses should create methods that
+// call RecordActivity to write into the log. |SetIsLogging|, |GetLogs|, and
+// |Clear| are called from the chrome://offline-internals page.
+//
+// Logging should be done by calling the corresponding subclass methods when
+// a loggable event occurs (i.e. when status has changed for a save request
+// or when an offlined page has been accessed/saved).
+//
+// This log only keeps track of the last |kMaxLogCount| events.
+class OfflineEventLogger {
+ public:
+  OfflineEventLogger();
+
+  ~OfflineEventLogger();
+
+  // Clears the recorded activities.
+  void Clear();
+
+  // Turns logging on/off.
+  void SetIsLogging(bool is_logging);
+
+  // Returns whether we are currently logging.
+  bool GetIsLogging();
+
+  // Dumps the current activity list into |records|.
+  void GetLogs(std::vector<std::string>* records);
+
+ protected:
+  // Write the activity into the cycling log if we are currently logging.
+  void RecordActivity(const std::string& activity);
+
+ private:
+  // Recorded offline page activities.
+  std::deque<std::string> activities_;
+
+  // Whether we are currently recording logs or not.
+  bool is_logging_;
+};
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_EVENT_LOGGER_H_