Add taskid for navigation, created in session sync

components/sync_sessions/sessions_sync_manager.cc

Index: components/sync_sessions/sessions_sync_manager.cc
diff --git a/components/sync_sessions/sessions_sync_manager.cc b/components/sync_sessions/sessions_sync_manager.cc
index d61d75591b9a75f8bf94956cfdbe0bec00c1797b..56c6740637a4b49e9f4ca4dd8bbbe6137eb3f745 100644
--- a/components/sync_sessions/sessions_sync_manager.cc
+++ b/components/sync_sessions/sessions_sync_manager.cc
@@ -136,7 +136,8 @@ SessionsSyncManager::SessionsSyncManager(
       local_event_router_(std::move(router)),
       page_revisit_broadcaster_(this, sessions_client),
       sessions_updated_callback_(sessions_updated_callback),
-      datatype_refresh_callback_(datatype_refresh_callback) {}
+      datatype_refresh_callback_(datatype_refresh_callback),
+      task_tracker_(base::MakeUnique<TaskTracker>()) {}
 
 SessionsSyncManager::~SessionsSyncManager() {}
 
@@ -399,6 +400,9 @@ void SessionsSyncManager::AssociateTab(SyncedTabDelegate* const tab_delegate,
   sync_pb::EntitySpecifics specifics;
   specifics.mutable_session()->CopyFrom(
       SessionTabToSpecifics(*session_tab, current_machine_tag(), tab_node_id));
+  // Intercept the sync model here to update task tracker and fill navigations
+  // with their ancestor navigations.
+  TrackTasks(tab_id, tab_delegate, specifics.mutable_session());
   syncer::SyncData data = syncer::SyncData::CreateLocalData(
       TabNodeIdToTag(current_machine_tag(), tab_node_id), current_session_name_,
       specifics);
@@ -418,6 +422,51 @@ void SessionsSyncManager::AssociateTab(SyncedTabDelegate* const tab_delegate,
   }
 }
 
+void SessionsSyncManager::TrackTasks(
+    SessionID::id_type tab_id,

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

given tab_id comes from tab_delegate, it seems like an unnecessary parameter?

[shenchao, 2017/04/11 18:53:44]

Done.

+    SyncedTabDelegate* const tab_delegate,
+    sync_pb::SessionSpecifics* session_specifics) {
+  sync_pb::SessionTab* tab_specifics = session_specifics->mutable_tab();
+  // Index in the whole navigations of the tab.
+  int current_navigation_index = tab_delegate->GetCurrentEntryIndex();
+  // Index in the tab_specifics, where the navigations is a -6/+6 window
+  int current_index_in_tab_specifics =
+      tab_specifics->current_navigation_index();
+
+  TabTasks* tab_tasks = task_tracker_->GetTabTasks(tab_id);
+  tab_tasks->UpdateWithNavigation(
+      current_navigation_index,
+      tab_delegate->GetTransitionAtIndex(current_navigation_index));
+
+  for (int i = 0; i < tab_specifics->navigation_size(); i++) {
+    // Excluding blocked navigations, which are appended at tail.
+    if (tab_specifics->navigation(i).blocked_state() ==
+        sync_pb::TabNavigation::STATE_BLOCKED) {
+      break;
+    }
+
+    int navigation_index =
+        current_navigation_index - current_index_in_tab_specifics + i;
+    // Skipping navigations not been tracked by task_tracker.
+    if (navigation_index < 0 ||
+        navigation_index >= tab_tasks->GetNavigationsCount()) {
+      continue;
+    }
+    std::vector<int64_t> task_ids =
+        tab_tasks->RootToSelfTaskIdsOfNavigationIndex(navigation_index);
+    if (task_ids.empty())
+      continue;
+
+    tab_specifics->mutable_navigation(i)->set_task_id(task_ids.back());
+    // Pop the task id of navigation self.
+    task_ids.pop_back();
+    for (auto ancestor_task_id : task_ids) {
+      tab_specifics->mutable_navigation(i)->add_ancestor_task_id(
+          ancestor_task_id);
+    }
+  }
+}
+
 bool SessionsSyncManager::RebuildAssociations() {
   syncer::SyncDataList data(sync_processor_->GetAllSyncData(syncer::SESSIONS));
   std::unique_ptr<syncer::SyncErrorFactory> error_handler(