Add taskid for navigation, created in session sync

components/sync_sessions/task_tracker.h

Index: components/sync_sessions/task_tracker.h
diff --git a/components/sync_sessions/task_tracker.h b/components/sync_sessions/task_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..9e3321656f4f678ecd7afb841eb13ea0ca5cc61d
--- /dev/null
+++ b/components/sync_sessions/task_tracker.h
@@ -0,0 +1,61 @@
+// 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/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 {
+
+// Tracks tasks of a tab.

[Patrick Noland, 2017/03/24 20:51:57]

Can you expand this comment? It's not currently explaining anything that the
name of the class doesn't communicate already.

[shenchao, 2017/03/25 23:53:13]

Done.

+class TabTasks {
+ public:
+  TabTasks();
+  virtual ~TabTasks();
+
+  // Return task id as a vector of int64_t for |nav_index|-th navigation of the
+  // tab.
+  std::vector<int64_t> GetTaskIdAtNav(int nav_index) const;

[Patrick Noland, 2017/03/24 20:51:57]

AtIndex or at AtNavIndex would be more descriptive

[shenchao, 2017/03/25 23:53:13]

Done.

+
+  int GetNavigationsNum() const { return ids_.size(); }

[Patrick Noland, 2017/03/24 20:51:57]

count or size would be more descriptive than Num

[shenchao, 2017/03/25 23:53:13]

Done.

+
+  // Updates the current task of the tab, given current navigation index of the
+  // tab as |current_nav_index|, and its transition |current_nav_transition|. If
+  // a new task is created, its id is (its parent task id, |new_id|).
+  void UpdateTask(int current_nav_index,
+                  ui::PageTransition current_nav_transition,
+                  int64_t new_id);

[Patrick Noland, 2017/03/24 20:51:57]

I'm a little confused that new_id is supplied as an argument. Why isn't the id
set by TabTasks?

[shenchao, 2017/03/25 23:53:13]

Done. I did that to make test easy but agree it was hacky. Injecting a clock
now.

+
+ private:
+  std::vector<int64_t> ids_;
+  int current_task_index_ = -1;
+};
+
+// Tracks tasks of current session.
+class TaskTracker {
+ public:
+  TaskTracker();
+  virtual ~TaskTracker();
+  // Returns a TabTasks pointer, which is owned by this object, for the tab of
+  // given |tab_id|.
+  TabTasks* GetTabTasks(SessionID::id_type tab_id);
+
+ private:
+  std::map<SessionID::id_type, std::unique_ptr<TabTasks>> local_tab_tasks_map_;
+};
+
+}  // namespace sync_sessions
+
+#endif  // COMPONENTS_SYNC_SESSIONS_TASK_TRACKER_H_