Add taskid for navigation, created in session sync

components/sync_sessions/task_tracker.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 COMPONENTS_SYNC_SESSIONS_TASK_TRACKER_H_
+#define COMPONENTS_SYNC_SESSIONS_TASK_TRACKER_H_
+
+#include <stddef.h>
+
+#include <map>
+#include <memory>
+#include <vector>
+
+#include "base/time/clock.h"
+#include "base/time/default_clock.h"
+#include "base/time/time.h"
+#include "components/sessions/core/session_id.h"
+#include "components/sessions/core/session_types.h"
+#include "components/sync_sessions/synced_tab_delegate.h"
+#include "ui/base/page_transition_types.h"
+
+namespace sync_sessions {
+
+// Class to generate and manage task ids for navigations of a tab. For each new
+// navigation of a tab,
+// UpdateTask(int current_nav_index,
+//            ui::PageTransition current_nav_transition,
+//            int64_t new_id)

[Nicolas Zea, 2017/03/27 20:43:52]

new_id doesn't seem to be a param anymore?

[shenchao, 2017/04/06 00:54:56]

Done.

+// needs to be called to update the objects.
+class TabTasks {
+ public:
+  explicit TabTasks(base::Clock* clock);
+  virtual ~TabTasks();
+
+  // Returns task id as a vector of int64_t for |nav_index|-th navigation of the
+  // tab.
+  std::vector<int64_t> GetTaskIdAtNavIndex(int nav_index) const;
+
+  int GetNavigationsCount() const { return ids_.size(); }
+
+  // Updates the current task of the tab, given current navigation index of the
+  // tab as |current_nav_index|, and its transition |current_nav_transition|.
+  void UpdateTask(int current_nav_index,
+                  ui::PageTransition current_nav_transition);

[Nicolas Zea, 2017/03/27 20:43:52]

Would be good to also explain what happens when a tab goes back/forward through
the nav stack. Presumably the current_nav_transition param is ignored?

[shenchao, 2017/04/06 00:54:56]

Actually the current_nav_transition param is not ignored but used to decided if
it's back/forward nav. Added comments.

+
+ private:
+  base::Clock* clock_;  // not owned
+  std::vector<int64_t> ids_;

[Nicolas Zea, 2017/03/27 20:43:53]

ids_ is pretty ambiguous. Perhaps call this task_ids_?

[shenchao, 2017/04/06 00:54:56]

Done.

+  int current_task_index_ = -1;

[Nicolas Zea, 2017/03/27 20:43:52]

Add DISALLOW_COPY_AND_ASSIGN macro (here and below)

[shenchao, 2017/04/06 00:54:56]

Done.

+};
+
+// Tracks tasks of current session.
+class TaskTracker {
+ public:
+  // Constructs with a clock to get timestamp as new task ids.
+  explicit TaskTracker(std::unique_ptr<base::Clock> clock =
+                           base::MakeUnique<base::DefaultClock>());
+  virtual ~TaskTracker();
+  // Returns a TabTasks pointer, which is owned by this object, for the tab of

[Nicolas Zea, 2017/03/27 20:43:53]

nit: newline above

[shenchao, 2017/04/06 00:54:55]

Done.

+  // given |tab_id|.
+  TabTasks* GetTabTasks(SessionID::id_type tab_id);
+
+ private:
+  std::unique_ptr<base::Clock> clock_;
+  std::map<SessionID::id_type, std::unique_ptr<TabTasks>> local_tab_tasks_map_;
+};
+
+}  // namespace sync_sessions
+
+#endif  // COMPONENTS_SYNC_SESSIONS_TASK_TRACKER_H_