drive: Event logger for chrome:drive-internals.

chrome/browser/chromeos/drive/event_logger.h

Index: chrome/browser/chromeos/drive/event_logger.h
diff --git a/chrome/browser/chromeos/drive/event_logger.h b/chrome/browser/chromeos/drive/event_logger.h
new file mode 100644
index 0000000000000000000000000000000000000000..e0341088aa29032e621c7428e4c9aabc9ea2f8cb
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+++ b/chrome/browser/chromeos/drive/event_logger.h
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+// Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_DRIVE_EVENT_LOGGER_H_
+#define CHROME_BROWSER_CHROMEOS_DRIVE_EVENT_LOGGER_H_
+
+#include <string>
+#include <deque>
+
+#include "base/basictypes.h"
+#include "base/time.h"
+
+namespace drive {
+
+// EventLogger is used to expose text messages to chrome:drive-internals,
+// for diagnosing the behavior of the Drive client.
+class EventLogger {
+ public:
+  // Represents a single event log.
+  struct Event {
+    Event(int id, const std::string& what);
+    int id;  // Monotonically increasing ID starting from 0.
+    base::Time when;  // When the event occurred.
+    std::string what;  // What happened.
+  };
+
+  // Creates an event logger that keeps the latest |history_size| events.
+  explicit EventLogger(size_t history_size);
+  ~EventLogger();
+
+  // Logs a message.
+  void Log(const std::string& what);
+
+  // Gets the list of latest events (the oldest event comes first).
+  const std::deque<Event>& history() const { return history_; }
+
+ private:
+  std::deque<Event> history_;
+  const size_t history_size_;
+  int next_event_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(EventLogger);
+};
+
+}  // namespace drive
+
+#endif  // CHROME_BROWSER_CHROMEOS_DRIVE_EVENT_LOGGER_H_