[SyncFS] Add TaskLogger and wire up it.

chrome/browser/sync_file_system/task_logger.h

Index: chrome/browser/sync_file_system/task_logger.h
diff --git a/chrome/browser/sync_file_system/task_logger.h b/chrome/browser/sync_file_system/task_logger.h
new file mode 100644
index 0000000000000000000000000000000000000000..a6e5f0a9ea6c0a92209719a342e45e6160117780
--- /dev/null
+++ b/chrome/browser/sync_file_system/task_logger.h
@@ -0,0 +1,63 @@
+// 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 CHROME_BROWSER_SYNC_FILE_SYSTEM_TASK_LOGGER_H_
+#define CHROME_BROWSER_SYNC_FILE_SYSTEM_TASK_LOGGER_H_
+
+#include <deque>
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/time/time.h"
+
+namespace sync_file_system {
+
+class TaskLogger : public base::SupportsWeakPtr<TaskLogger> {
+ public:
+  struct TaskLog {
+    base::TimeDelta duration;
+    std::string type;
+    std::string summary;
+    std::vector<std::string> details;
+
+    TaskLog();
+    ~TaskLog();
+  };
+
+  class Observer {
+   public:
+    virtual void OnLogRecorded(const TaskLog& task_log) = 0;
+
+   protected:
+    Observer() {}
+    virtual ~Observer() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Observer);
+  };
+
+  TaskLogger();
+  ~TaskLogger();
+
+  void RecordLog(scoped_ptr<TaskLog> log);
+  void ClearLog();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  const std::deque<TaskLog*>& GetLog() const;
+
+ private:
+  std::deque<TaskLog*> log_history_;
+
+  ObserverList<Observer> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskLogger);
+};
+
+}  // namespace sync_file_system
+
+#endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_TASK_LOGGER_H_