Add taskid for navigation, created in session sync

components/sync_sessions/task_tracker.cc

+// 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.
+
+#include "components/sync_sessions/task_tracker.h"
+
+namespace sync_sessions {
+
+TabTasks::TabTasks() {}
+
+TabTasks::~TabTasks() {}
+
+std::vector<int64_t> TabTasks::GetTaskIdAtNav(int nav_index) const {
+  CHECK(nav_index >= 0 && (unsigned)nav_index < ids_.size());
+  std::vector<int64_t> id;
+  for (int i = 0; i <= nav_index; i++) {
+    if (ids_[i] != -1)
+      id.push_back(ids_[i]);
+  }
+  return id;
+}
+
+void TabTasks::UpdateTask(int current_nav_index,
+                          ui::PageTransition current_nav_transition,
+                          int64_t new_id) {
+  // Assuming the first navigation is chrome://newtab

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

Is that always true? What about links opened in a new tab or window?

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

Not unless the if-condition is true. Added comment to clarify. 

+  if (current_nav_index == 1 && current_task_index_ == -1) {
+    ids_.push_back(-1);
+    current_task_index_ = 0;
+  }
+
+  // Trigger by some notifications on the current page, do nothing.
+  if (current_nav_index < 0 || current_nav_index == current_task_index_) {
+    DVLOG(1) << "Doing nothing";
+    return;
+  }
+
+  // Back to some previous navigation or forward to some future navigation after
+  // going back.
+  if (current_nav_index < current_task_index_ ||
+      (current_nav_index > current_task_index_ &&
+       current_nav_transition & ui::PAGE_TRANSITION_FORWARD_BACK &&
+       (unsigned)current_nav_index < ids_.size())) {
+    DVLOG(1) << "Just updating task depth.";
+    current_task_index_ = current_nav_index;
+    return;
+  }
+
+  // a new navigation
+  if (current_nav_index == current_task_index_ + 1) {

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

This doesn't seem to account for transitions that start new tasks

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

current_nav_index == current_task_index_ + 1 && current_nav_transition &
ui::PAGE_TRANSITION_FORWARD_BACK 
is covered by previous if. Could you help me find out what else I missed? Thanks

+    DVLOG(1) << "Creating a task.";
+    current_task_index_ = current_nav_index;
+    ids_.erase(ids_.begin() + current_nav_index, ids_.end());
+    ids_.push_back(new_id);
+    return;
+  }
+}
+
+TaskTracker::TaskTracker() {}
+
+TaskTracker::~TaskTracker() {}
+
+TabTasks* TaskTracker::GetTabTasks(SessionID::id_type tab_id) {
+  if (local_tab_tasks_map_.find(tab_id) == local_tab_tasks_map_.end()) {
+    local_tab_tasks_map_[tab_id] = base::MakeUnique<TabTasks>();
+  }
+  return local_tab_tasks_map_[tab_id].get();
+}
+
+}  // namespace sync_sessions