Add taskid for navigation, created in session sync

components/sync_sessions/task_tracker.cc

Index: components/sync_sessions/task_tracker.cc
diff --git a/components/sync_sessions/task_tracker.cc b/components/sync_sessions/task_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0f8902e2905383a98113746e138927b4909e1d7c
--- /dev/null
+++ b/components/sync_sessions/task_tracker.cc
@@ -0,0 +1,173 @@
+// 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"
+
+#include <utility>
+
+#include "base/numerics/safe_conversions.h"
+
+namespace sync_sessions {
+
+namespace {
+// The maximum number of tasks we track in a tab.
+int kMaxNumTasksPerTab = 100;
+}
+
+TabTasks::TabTasks() {}
+
+TabTasks::~TabTasks() {}
+
+std::vector<int64_t> TabTasks::GetTaskIdsForNavigation(
+    int navigation_index) const {
+  CHECK_LE(0, navigation_index);
+  CHECK_LT(navigation_index, GetNavigationsCount());
+
+  std::vector<int64_t> root_to_self_task_ids;
+  // Position of the navigation in task_ids_ vector.
+  int navigation_position = navigation_index - excluded_navigation_num_;
+
+  // If navigation_index is an excluded ancestor task, returns empty.
+  if (navigation_position < 0)
+    return root_to_self_task_ids;
+
+  TaskIdAndRoot task_id_and_root = task_ids_[navigation_position];
+
+  // If navigation_index is an invalid task, returns empty.
+  if (task_id_and_root.root_navigation_index < 0)
+    return root_to_self_task_ids;
+
+  // The root task can be excluded. If so, consider the oldest ancestor
+  // available as root.
+  int root_navigation_index =
+      task_id_and_root.root_navigation_index > excluded_navigation_num_
+          ? task_id_and_root.root_navigation_index - excluded_navigation_num_
+          : 0;
+  for (int i = root_navigation_index; i <= navigation_position; i++) {
+    // Fills the vector with valid tasks.
+    if (task_ids_[i].root_navigation_index >= 0)
+      root_to_self_task_ids.push_back(task_ids_[i].task_id);
+  }
+  return root_to_self_task_ids;
+}
+
+int TabTasks::GetNavigationsCount() const {
+  return excluded_navigation_num_ + task_ids_.size();
+}
+
+void TabTasks::UpdateWithNavigation(int navigation_index,
+                                    ui::PageTransition transition,
+                                    int64_t navigation_id) {
+  // Triggered by some notifications on the current page, do nothing.
+  if (navigation_index == current_navigation_index_) {
+    DVLOG(1) << "Doing nothing for navigation_index: " << navigation_index
+             << " of transition: " << transition;
+    return;
+  }
+
+  // Going back/forward to some previous navigation.
+  if (navigation_index < current_navigation_index_ ||
+      (navigation_index > current_navigation_index_ &&
+       transition & ui::PAGE_TRANSITION_FORWARD_BACK &&
+       base::checked_cast<size_t>(navigation_index) < task_ids_.size())) {
+    DVLOG(1) << "Just updating task position with navigation_index: "
+             << navigation_index << " of transition: " << transition;
+    current_navigation_index_ = navigation_index;
+    return;
+  }
+
+  // A new task for the new navigation.
+  int root_navigation_index = navigation_index;
+  if (current_navigation_index_ != -1 &&
+      (ui::PageTransitionCoreTypeIs(transition, ui::PAGE_TRANSITION_LINK) ||
+       ui::PageTransitionCoreTypeIs(transition,
+                                    ui::PAGE_TRANSITION_AUTO_SUBFRAME) ||
+       ui::PageTransitionCoreTypeIs(transition,
+                                    ui::PAGE_TRANSITION_MANUAL_SUBFRAME) ||
+       ui::PageTransitionCoreTypeIs(transition,
+                                    ui::PAGE_TRANSITION_FORM_SUBMIT) ||
+       transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK)) {
+    // Creating a sub-task with navigation at current_navigation_index as
+    // parent.
+    DVLOG(1) << "Creating a sub-task with navigation_index: "
+             << navigation_index << " of transition: " << transition
+             << " under navigation_index: " << current_navigation_index_;
+    // Position in task_id_.
+    int current_navigation_position =
+        current_navigation_index_ - excluded_navigation_num_;
+    // If current/parent task is excluded, consider the new task as a root task.
+    if (current_navigation_position >= 0) {
+      CHECK_LT(current_navigation_position,
+               base::checked_cast<int>(task_ids_.size()));
+      root_navigation_index =
+          task_ids_[current_navigation_position].root_navigation_index;
+    } else {
+      DVLOG(1) << "Becaue parent task is excluded, consider the sub-task as a "
+                  "root task.";
+    }
+  } else {
+    // Creating a root task.
+    // For now, we don't consider tasks cross tabs, so first navigation of the
+    // tab always creates a root task.
+    DVLOG(1) << "Creating a root task with navigation_index: "
+             << navigation_index << " of transition: " << transition;
+  }
+
+  // In most cases navigation_index == excluded_navigation_num_ +
+  // task_ids_.size() if the previous navigation is end of chain, or
+  // navigation_index < excluded_navigation_num_ + task_ids_.size() otherwise.
+  // In few case navigation_index > excluded_navigation_num_ + task_ids_.size(),
+  // we fill task_ids_ with invalid contents. A known case is the first
+  // navigation after newtab.
+  for (int i = task_ids_.size() + excluded_navigation_num_;
+       i < navigation_index; i++) {
+    task_ids_.push_back({-1, -1});
+  }
+
+  // Erase all task ids associated with an outdated forward navigation stack.
+  if (navigation_index > excluded_navigation_num_) {
+    int new_task_id_position = navigation_index - excluded_navigation_num_;
+    task_ids_.erase(task_ids_.begin() + new_task_id_position, task_ids_.end());
+  } else {
+    excluded_navigation_num_ = navigation_index;
+    // new task id position is 0
+    task_ids_.clear();
+  }
+
+  // Exclude oldest ancestors if task number reaches the limit.
+  int more_tasks_number = task_ids_.size() + 1 - kMaxNumTasksPerTab;
+  if (more_tasks_number > 0) {
+    task_ids_.erase(task_ids_.begin(), task_ids_.begin() + more_tasks_number);
+    DVLOG(1) << "Excluding " << more_tasks_number
+             << " oldest ancestor(s) from navigation index "
+             << excluded_navigation_num_;
+    excluded_navigation_num_ += more_tasks_number;
+  }
+
+  TaskIdAndRoot new_task = {root_navigation_index, navigation_id};
+  // Add the current task at navigation_index.
+  task_ids_.push_back(new_task);
+  current_navigation_index_ = navigation_index;
+  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();
+}
+
+void TaskTracker::CleanTabTasks(SessionID::id_type tab_id) {
+  auto iter = local_tab_tasks_map_.find(tab_id);
+  if (iter != local_tab_tasks_map_.end()) {
+    local_tab_tasks_map_.erase(iter);
+  }
+}
+
+}  // namespace sync_sessions