[Sync] Restore previous session if no tabbed windows present

components/sync_sessions/synced_session_tracker.cc

 // Copyright (c) 2012 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/synced_session_tracker.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 203 matching lines @@
   unmapped_tabs_[session_tag].clear();
 }
 
 bool SyncedSessionTracker::IsTabUnmappedForTesting(SessionID::id_type tab_id) {
   auto it = unmapped_tabs_[local_session_tag_].find(tab_id);
   return it != unmapped_tabs_[local_session_tag_].end();
 }
 
 void SyncedSessionTracker::PutWindowInSession(const std::string& session_tag,
                                               SessionID::id_type window_id) {
+  if (GetSession(session_tag)->windows.find(window_id) !=
+      GetSession(session_tag)->windows.end()) {
+    DVLOG(1) << "Window " << window_id << " already added to session "
+             << session_tag;
+    return;
+  }
   std::unique_ptr<SyncedSessionWindow> window;
 
   auto iter = unmapped_windows_[session_tag].find(window_id);
   if (iter != unmapped_windows_[session_tag].end()) {
     DCHECK_EQ(synced_window_map_[session_tag][window_id], iter->second.get());
     window = std::move(iter->second);
     unmapped_windows_[session_tag].erase(iter);
     DVLOG(1) << "Putting seen window " << window_id << " at " << window.get()
              << "in " << (session_tag == local_session_tag_ ? "local session"
                                                             : session_tag);
@@ skipping 104 matching lines @@
     DVLOG(1) << "Getting "
              << (session_tag == local_session_tag_ ? "local session"
                                                    : session_tag)
              << "'s new tab " << tab_id << " at " << tab_ptr;
   }
   DCHECK(tab_ptr);
   DCHECK_EQ(tab_ptr->tab_id.id(), tab_id);
   return tab_ptr;
 }
 
-void SyncedSessionTracker::CleanupForeignSession(
-    const std::string& session_tag) {
-  DCHECK_NE(local_session_tag_, session_tag);
+void SyncedSessionTracker::CleanupSession(const std::string& session_tag) {
   CleanupSessionImpl(session_tag);
 }
 
 void SyncedSessionTracker::CleanupLocalTabs(std::set<int>* deleted_node_ids) {
   DCHECK(!local_session_tag_.empty());
   for (const auto& tab_pair : unmapped_tabs_[local_session_tag_])
     local_tab_pool_.FreeTab(tab_pair.first);
   CleanupSessionImpl(local_session_tag_);
   local_tab_pool_.CleanupTabNodes(deleted_node_ids);
   for (int tab_node_id : *deleted_node_ids) {
     GetSession(local_session_tag_)->tab_node_ids.erase(tab_node_id);
   }
 }
 
 bool SyncedSessionTracker::GetTabNodeFromLocalTabId(SessionID::id_type tab_id,
                                                     int* tab_node_id) {
   DCHECK(!local_session_tag_.empty());
-  // Ensure a placeholder SessionTab is in place, if not already.
-  // Although we don't need a SessionTab to fulfill this request, this forces
-  // the
-  // creation of one if it doesn't already exist. This helps to make sure we're
-  // tracking this |tab_id| if |local_tab_pool_| is, and everyone's data
-  // structures
-  // are kept in sync and as consistent as possible.
+  // Ensure a placeholder SessionTab is in place, if not already. Although we
+  // don't need a SessionTab to fulfill this request, this forces the creation
+  // of one if it doesn't already exist. This helps to make sure we're tracking
+  // this |tab_id| if |local_tab_pool_| is, and everyone's data structures are
+  // kept in sync and as consistent as possible.
   GetTab(local_session_tag_, tab_id);  // Ignore result.
 
   bool reused_existing_tab =
       local_tab_pool_.GetTabNodeForTab(tab_id, tab_node_id);
   DCHECK_NE(TabNodePool::kInvalidTabNodeID, *tab_node_id);
   GetSession(local_session_tag_)->tab_node_ids.insert(*tab_node_id);
   return reused_existing_tab;
 }
 
 bool SyncedSessionTracker::IsLocalTabNodeAssociated(int tab_node_id) {
@@ skipping 63 matching lines @@
   // Get rid of our convenience maps (does not delete the actual Window/Tabs
   // themselves; they should have all been deleted above).
   synced_window_map_.clear();
   synced_tab_map_.clear();
 
   local_tab_pool_.Clear();
   local_session_tag_.clear();
 }
 
 }  // namespace sync_sessions