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
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index 0000000000000000000000000000000000000000..40f452118b438daa835c8d06234faed3703659b8
--- /dev/null
+++ b/components/sync_sessions/task_tracker.h
@@ -0,0 +1,93 @@
+// 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
+// current navigation of a tab, UpdateWithNavigation(int navigation_index,
+//            ui::PageTransition transition)
+// needs to be called to update the object.
+//
+// TODO(shenchao): If the tab is restored, then the input navigation is not
+// necessary the first navigation in this case. Need to fix it by initalizing

[Nicolas Zea, 2017/04/10 17:09:01]

nit: necessary -> necessarily

[shenchao, 2017/04/11 18:53:45]

Done.

+// the object with restored data.
+// TODO(shenchao): Support to track tasks cross tabs.
+class TabTasks {
+ public:
+  explicit TabTasks(base::Clock* clock);
+  virtual ~TabTasks();
+
+  // Returns top-down task id list of ancestors and itself as a vector for
+  // |navigation_index|-th navigation of the tab.
+  std::vector<int64_t> RootToSelfTaskIdsOfNavigationIndex(

[Nicolas Zea, 2017/04/10 17:09:00]

This name is pretty tough to understand. How about just GetTaskIdsForNavigation?

[shenchao, 2017/04/11 18:53:45]

Done.

+      int navigation_index) const;
+
+  int GetNavigationsCount() const { return task_ids_.size(); }
+
+  // Updates the current task of the tab, given current navigation index of the
+  // tab as |navigation_index|, and its |transition|.
+  // If the navigation is from going back/forward of the tab, we set its first
+  // visit as current task; if the navigation is new, we create a subtask of the
+  // previous navigation if it's linked from the previous one or a root task
+  // otherwise.
+  void UpdateWithNavigation(int64_t navigation_index,
+                            ui::PageTransition transition);
+
+ private:
+  struct TaskIdAndRoot {
+    // Root task index in task_ids_. Negative value means it's an invalid task
+    // just for filling the task_ids_.
+    int root_navigation_index;
+    int64_t task_id;
+  };
+
+  base::Clock* clock_;
+  // Task ids (with root task) for the navigations of the tab. The vector is
+  // corresponding to the sequence of navigations of the tab.
+  std::vector<TaskIdAndRoot> task_ids_;
+  // Index of current navigation in task_ids_.
+  int64_t current_navigation_index_ = -1;
+
+  DISALLOW_COPY_AND_ASSIGN(TabTasks);
+};
+
+// 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
+  // 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_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskTracker);
+};
+
+}  // namespace sync_sessions
+
+#endif  // COMPONENTS_SYNC_SESSIONS_TASK_TRACKER_H_