chrome/browser/sync/sessions/sessions_sync_manager.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/sync/sessions/sessions_sync_manager.h"
   6
   7 #include "base/metrics/field_trial.h"
   8 #include "chrome/browser/chrome_notification_types.h"
   9 #include "chrome/browser/favicon/favicon_service_factory.h"
  10 #include "chrome/browser/history/history_service_factory.h"
  11 #include "chrome/browser/profiles/profile.h"
  12 #include "chrome/browser/search/search.h"
  13 #include "chrome/browser/sync/glue/synced_tab_delegate.h"
  14 #include "chrome/browser/sync/glue/synced_window_delegate.h"
  15 #include "chrome/browser/sync/sessions/synced_window_delegates_getter.h"
  16 #include "chrome/common/url_constants.h"
  17 #include "components/sessions/content/content_serialized_navigation_builder.h"
  18 #include "components/sync_driver/local_device_info_provider.h"
  19 #include "content/public/browser/favicon_status.h"
  20 #include "content/public/browser/navigation_entry.h"
  21 #include "content/public/browser/notification_details.h"
  22 #include "content/public/browser/notification_service.h"
  23 #include "content/public/browser/notification_source.h"
  24 #include "content/public/common/url_constants.h"
  25 #include "sync/api/sync_error.h"
  26 #include "sync/api/sync_error_factory.h"
  27 #include "sync/api/sync_merge_result.h"
  28 #include "sync/api/time.h"
  29
  30 using content::NavigationEntry;
  31 using sessions::ContentSerializedNavigationBuilder;
  32 using sessions::SerializedNavigationEntry;
  33 using sync_driver::DeviceInfo;
  34 using sync_driver::LocalDeviceInfoProvider;
  35 using syncer::SyncChange;
  36 using syncer::SyncData;
  37
  38 namespace browser_sync {
  39
  40 namespace {
  41
  42 // Maximum number of favicons to sync.
  43 // TODO(zea): pull this from the server.
  44 const int kMaxSyncFavicons = 200;
  45
  46 // The maximum number of navigations in each direction we care to sync.
  47 const int kMaxSyncNavigationCount = 6;
  48
  49 // The URL at which the set of synced tabs is displayed. We treat it differently
  50 // from all other URL's as accessing it triggers a sync refresh of Sessions.
  51 const char kNTPOpenTabSyncURL[] = "chrome://newtab/#open_tabs";
  52
  53 // Default number of days without activity after which a session is considered
  54 // stale and becomes a candidate for garbage collection.
  55 const size_t kDefaultStaleSessionThresholdDays = 14;  // 2 weeks.
  56
  57 // Comparator function for use with std::sort that will sort tabs by
  58 // descending timestamp (i.e., most recent first).
  59 bool TabsRecencyComparator(const sessions::SessionTab* t1,
  60                            const sessions::SessionTab* t2) {
  61   return t1->timestamp > t2->timestamp;
  62 }
  63
  64 // Comparator function for use with std::sort that will sort sessions by
  65 // descending modified_time (i.e., most recent first).
  66 bool SessionsRecencyComparator(const sync_driver::SyncedSession* s1,
  67                            const sync_driver::SyncedSession* s2) {
  68   return s1->modified_time > s2->modified_time;
  69 }
  70
  71 }  // namespace
  72
  73 // |local_device| is owned by ProfileSyncService, its lifetime exceeds
  74 // lifetime of SessionSyncManager.
  75 SessionsSyncManager::SessionsSyncManager(
  76     Profile* profile,
  77     LocalDeviceInfoProvider* local_device,
  78     scoped_ptr<LocalSessionEventRouter> router,
  79     scoped_ptr<SyncedWindowDelegatesGetter> synced_window_getter)
  80     : favicon_cache_(FaviconServiceFactory::GetForProfile(
  81                          profile,
  82                          ServiceAccessType::EXPLICIT_ACCESS),
  83                      HistoryServiceFactory::GetForProfile(
  84                          profile,
  85                          ServiceAccessType::EXPLICIT_ACCESS),
  86                      kMaxSyncFavicons),
  87       local_tab_pool_out_of_sync_(true),
  88       sync_prefs_(profile->GetPrefs()),
  89       profile_(profile),
  90       local_device_(local_device),
  91       local_session_header_node_id_(TabNodePool::kInvalidTabNodeID),
  92       stale_session_threshold_days_(kDefaultStaleSessionThresholdDays),
  93       local_event_router_(router.Pass()),
  94       synced_window_getter_(synced_window_getter.Pass()) {}
  95
  96 LocalSessionEventRouter::~LocalSessionEventRouter() {}
  97
  98 SessionsSyncManager::~SessionsSyncManager() {
  99 }
 100
 101 // Returns the GUID-based string that should be used for
 102 // |SessionsSyncManager::current_machine_tag_|.
 103 static std::string BuildMachineTag(const std::string& cache_guid) {
 104   std::string machine_tag = "session_sync";
 105   machine_tag.append(cache_guid);
 106   return machine_tag;
 107 }
 108
 109 syncer::SyncMergeResult SessionsSyncManager::MergeDataAndStartSyncing(
 110      syncer::ModelType type,
 111      const syncer::SyncDataList& initial_sync_data,
 112      scoped_ptr<syncer::SyncChangeProcessor> sync_processor,
 113      scoped_ptr<syncer::SyncErrorFactory> error_handler) {
 114   syncer::SyncMergeResult merge_result(type);
 115   DCHECK(session_tracker_.Empty());
 116   DCHECK_EQ(0U, local_tab_pool_.Capacity());
 117
 118   error_handler_ = error_handler.Pass();
 119   sync_processor_ = sync_processor.Pass();
 120
 121   local_session_header_node_id_ = TabNodePool::kInvalidTabNodeID;
 122
 123   // Make sure we have a machine tag.  We do this now (versus earlier) as it's
 124   // a conveniently safe time to assert sync is ready and the cache_guid is
 125   // initialized.
 126   if (current_machine_tag_.empty()) {
 127     InitializeCurrentMachineTag();
 128   }
 129
 130   // SessionDataTypeController ensures that the local device info
 131   // is available before activating this datatype.
 132   DCHECK(local_device_);
 133   const DeviceInfo* local_device_info = local_device_->GetLocalDeviceInfo();
 134   if (local_device_info) {
 135     current_session_name_ = local_device_info->client_name();
 136   } else {
 137     merge_result.set_error(error_handler_->CreateAndUploadError(
 138         FROM_HERE,
 139         "Failed to get local device info."));
 140     return merge_result;
 141   }
 142
 143   session_tracker_.SetLocalSessionTag(current_machine_tag_);
 144
 145   syncer::SyncChangeList new_changes;
 146
 147   // First, we iterate over sync data to update our session_tracker_.
 148   syncer::SyncDataList restored_tabs;
 149   if (!InitFromSyncModel(initial_sync_data, &restored_tabs, &new_changes)) {
 150     // The sync db didn't have a header node for us. Create one.
 151     sync_pb::EntitySpecifics specifics;
 152     sync_pb::SessionSpecifics* base_specifics = specifics.mutable_session();
 153     base_specifics->set_session_tag(current_machine_tag());
 154     sync_pb::SessionHeader* header_s = base_specifics->mutable_header();
 155     header_s->set_client_name(current_session_name_);
 156     header_s->set_device_type(local_device_info->device_type());
 157     syncer::SyncData data = syncer::SyncData::CreateLocalData(
 158         current_machine_tag(), current_session_name_, specifics);
 159     new_changes.push_back(syncer::SyncChange(
 160         FROM_HERE, syncer::SyncChange::ACTION_ADD, data));
 161   }
 162
 163 #if defined(OS_ANDROID)
 164   std::string sync_machine_tag(BuildMachineTag(
 165       local_device_->GetLocalSyncCacheGUID()));
 166   if (current_machine_tag_.compare(sync_machine_tag) != 0)
 167     DeleteForeignSessionInternal(sync_machine_tag, &new_changes);
 168 #endif
 169
 170   // Check if anything has changed on the local client side.
 171   AssociateWindows(RELOAD_TABS, restored_tabs, &new_changes);
 172   local_tab_pool_out_of_sync_ = false;
 173
 174   merge_result.set_error(
 175       sync_processor_->ProcessSyncChanges(FROM_HERE, new_changes));
 176
 177   local_event_router_->StartRoutingTo(this);
 178   return merge_result;
 179 }
 180
 181 void SessionsSyncManager::AssociateWindows(
 182     ReloadTabsOption option,
 183     const syncer::SyncDataList& restored_tabs,
 184     syncer::SyncChangeList* change_output) {
 185   const std::string local_tag = current_machine_tag();
 186   sync_pb::SessionSpecifics specifics;
 187   specifics.set_session_tag(local_tag);
 188   sync_pb::SessionHeader* header_s = specifics.mutable_header();
 189   sync_driver::SyncedSession* current_session =
 190       session_tracker_.GetSession(local_tag);
 191   current_session->modified_time = base::Time::Now();
 192   header_s->set_client_name(current_session_name_);
 193   // SessionDataTypeController ensures that the local device info
 194   // is available before activating this datatype.
 195   DCHECK(local_device_);
 196   const DeviceInfo* local_device_info = local_device_->GetLocalDeviceInfo();
 197   header_s->set_device_type(local_device_info->device_type());
 198
 199   session_tracker_.ResetSessionTracking(local_tag);
 200   std::set<const SyncedWindowDelegate*> windows =
 201       synced_window_getter_->GetSyncedWindowDelegates();
 202
 203   for (std::set<const SyncedWindowDelegate*>::const_iterator i =
 204            windows.begin(); i != windows.end(); ++i) {
 205     // Make sure the window has tabs and a viewable window. The viewable window
 206     // check is necessary because, for example, when a browser is closed the
 207     // destructor is not necessarily run immediately. This means its possible
 208     // for us to get a handle to a browser that is about to be removed. If
 209     // the tab count is 0 or the window is NULL, the browser is about to be
 210     // deleted, so we ignore it.
 211     if ((*i)->ShouldSync() && (*i)->GetTabCount() && (*i)->HasWindow()) {
 212       sync_pb::SessionWindow window_s;
 213       SessionID::id_type window_id = (*i)->GetSessionId();
 214       DVLOG(1) << "Associating window " << window_id << " with "
 215                << (*i)->GetTabCount() << " tabs.";
 216       window_s.set_window_id(window_id);
 217       // Note: We don't bother to set selected tab index anymore. We still
 218       // consume it when receiving foreign sessions, as reading it is free, but
 219       // it triggers too many sync cycles with too little value to make setting
 220       // it worthwhile.
 221       if ((*i)->IsTypeTabbed()) {
 222         window_s.set_browser_type(
 223             sync_pb::SessionWindow_BrowserType_TYPE_TABBED);
 224       } else {
 225         window_s.set_browser_type(
 226             sync_pb::SessionWindow_BrowserType_TYPE_POPUP);
 227       }
 228
 229       bool found_tabs = false;
 230       for (int j = 0; j < (*i)->GetTabCount(); ++j) {
 231         SessionID::id_type tab_id = (*i)->GetTabIdAt(j);
 232         SyncedTabDelegate* synced_tab = (*i)->GetTabAt(j);
 233
 234         // GetTabAt can return a null tab; in that case just skip it.
 235         if (!synced_tab)
 236           continue;
 237
 238         if (!synced_tab->HasWebContents()) {
 239           // For tabs without WebContents update the |tab_id|, as it could have
 240           // changed after a session restore.
 241           // Note: We cannot check if a tab is valid if it has no WebContents.
 242           // We assume any such tab is valid and leave the contents of
 243           // corresponding sync node unchanged.
 244           if (synced_tab->GetSyncId() > TabNodePool::kInvalidTabNodeID &&
 245               tab_id > TabNodePool::kInvalidTabID) {
 246             AssociateRestoredPlaceholderTab(*synced_tab, tab_id,
 247                                             restored_tabs, change_output);
 248             found_tabs = true;
 249             window_s.add_tab(tab_id);
 250           }
 251           continue;
 252         }
 253
 254         if (RELOAD_TABS == option)
 255           AssociateTab(synced_tab, change_output);
 256
 257         // If the tab is valid, it would have been added to the tracker either
 258         // by the above AssociateTab call (at association time), or by the
 259         // change processor calling AssociateTab for all modified tabs.
 260         // Therefore, we can key whether this window has valid tabs based on
 261         // the tab's presence in the tracker.
 262         const sessions::SessionTab* tab = NULL;
 263         if (session_tracker_.LookupSessionTab(local_tag, tab_id, &tab)) {
 264           found_tabs = true;
 265           window_s.add_tab(tab_id);
 266         }
 267       }
 268       if (found_tabs) {
 269         sync_pb::SessionWindow* header_window = header_s->add_window();
 270         *header_window = window_s;
 271
 272         // Update this window's representation in the synced session tracker.
 273         session_tracker_.PutWindowInSession(local_tag, window_id);
 274         BuildSyncedSessionFromSpecifics(local_tag,
 275                                         window_s,
 276                                         current_session->modified_time,
 277                                         current_session->windows[window_id]);
 278       }
 279     }
 280   }
 281   local_tab_pool_.DeleteUnassociatedTabNodes(change_output);
 282   session_tracker_.CleanupSession(local_tag);
 283
 284   // Always update the header.  Sync takes care of dropping this update
 285   // if the entity specifics are identical (i.e windows, client name did
 286   // not change).
 287   sync_pb::EntitySpecifics entity;
 288   entity.mutable_session()->CopyFrom(specifics);
 289   syncer::SyncData data = syncer::SyncData::CreateLocalData(
 290         current_machine_tag(), current_session_name_, entity);
 291   change_output->push_back(syncer::SyncChange(
 292         FROM_HERE, syncer::SyncChange::ACTION_UPDATE, data));
 293 }
 294
 295 void SessionsSyncManager::AssociateTab(SyncedTabDelegate* const tab,
 296                                        syncer::SyncChangeList* change_output) {
 297   DCHECK(tab->HasWebContents());
 298   SessionID::id_type tab_id = tab->GetSessionId();
 299   if (tab->profile() != profile_)
 300     return;
 301
 302   if (tab->IsBeingDestroyed()) {
 303     // This tab is closing.
 304     TabLinksMap::iterator tab_iter = local_tab_map_.find(tab_id);
 305     if (tab_iter == local_tab_map_.end()) {
 306       // We aren't tracking this tab (for example, sync setting page).
 307       return;
 308     }
 309     local_tab_pool_.FreeTabNode(tab_iter->second->tab_node_id(),
 310                                 change_output);
 311     local_tab_map_.erase(tab_iter);
 312     return;
 313   }
 314
 315   if (!tab->ShouldSync())
 316     return;
 317
 318   TabLinksMap::iterator local_tab_map_iter = local_tab_map_.find(tab_id);
 319   TabLink* tab_link = NULL;
 320
 321   if (local_tab_map_iter == local_tab_map_.end()) {
 322     int tab_node_id = tab->GetSyncId();
 323     // If there is an old sync node for the tab, reuse it.  If this is a new
 324     // tab, get a sync node for it.
 325     if (!local_tab_pool_.IsUnassociatedTabNode(tab_node_id)) {
 326       tab_node_id = local_tab_pool_.GetFreeTabNode(change_output);
 327       tab->SetSyncId(tab_node_id);
 328     }
 329     local_tab_pool_.AssociateTabNode(tab_node_id, tab_id);
 330     tab_link = new TabLink(tab_node_id, tab);
 331     local_tab_map_[tab_id] = make_linked_ptr<TabLink>(tab_link);
 332   } else {
 333     // This tab is already associated with a sync node, reuse it.
 334     // Note: on some platforms the tab object may have changed, so we ensure
 335     // the tab link is up to date.
 336     tab_link = local_tab_map_iter->second.get();
 337     local_tab_map_iter->second->set_tab(tab);
 338   }
 339   DCHECK(tab_link);
 340   DCHECK_NE(tab_link->tab_node_id(), TabNodePool::kInvalidTabNodeID);
 341   DVLOG(1) << "Reloading tab " << tab_id << " from window "
 342            << tab->GetWindowId();
 343
 344   // Write to sync model.
 345   sync_pb::EntitySpecifics specifics;
 346   LocalTabDelegateToSpecifics(*tab, specifics.mutable_session());
 347   syncer::SyncData data = syncer::SyncData::CreateLocalData(
 348       TabNodePool::TabIdToTag(current_machine_tag_,
 349                                tab_link->tab_node_id()),
 350       current_session_name_,
 351       specifics);
 352   change_output->push_back(syncer::SyncChange(
 353       FROM_HERE, syncer::SyncChange::ACTION_UPDATE, data));
 354
 355   const GURL new_url = GetCurrentVirtualURL(*tab);
 356   if (new_url != tab_link->url()) {
 357     tab_link->set_url(new_url);
 358     favicon_cache_.OnFaviconVisited(new_url, GetCurrentFaviconURL(*tab));
 359   }
 360
 361   session_tracker_.GetSession(current_machine_tag())->modified_time =
 362       base::Time::Now();
 363 }
 364
 365 void SessionsSyncManager::RebuildAssociations() {
 366   syncer::SyncDataList data(
 367       sync_processor_->GetAllSyncData(syncer::SESSIONS));
 368   scoped_ptr<syncer::SyncErrorFactory> error_handler(error_handler_.Pass());
 369   scoped_ptr<syncer::SyncChangeProcessor> processor(sync_processor_.Pass());
 370
 371   StopSyncing(syncer::SESSIONS);
 372   MergeDataAndStartSyncing(
 373       syncer::SESSIONS, data, processor.Pass(), error_handler.Pass());
 374 }
 375
 376 bool SessionsSyncManager::IsValidSessionHeader(
 377     const sync_pb::SessionHeader& header) {
 378   // Verify that tab IDs appear only once within a session.
 379   // Intended to prevent http://crbug.com/360822.
 380   std::set<int> session_tab_ids;
 381   for (int i = 0; i < header.window_size(); ++i) {
 382     const sync_pb::SessionWindow& window = header.window(i);
 383     for (int j = 0; j < window.tab_size(); ++j) {
 384       const int tab_id = window.tab(j);
 385       bool success = session_tab_ids.insert(tab_id).second;
 386       if (!success)
 387         return false;
 388     }
 389   }
 390
 391   return true;
 392 }
 393
 394 void SessionsSyncManager::OnLocalTabModified(SyncedTabDelegate* modified_tab) {
 395   const content::NavigationEntry* entry = modified_tab->GetActiveEntry();
 396   if (!modified_tab->IsBeingDestroyed() &&
 397       entry &&
 398       entry->GetVirtualURL().is_valid() &&
 399       entry->GetVirtualURL().spec() == kNTPOpenTabSyncURL) {
 400     DVLOG(1) << "Triggering sync refresh for sessions datatype.";
 401     const syncer::ModelTypeSet types(syncer::SESSIONS);
 402     content::NotificationService::current()->Notify(
 403         chrome::NOTIFICATION_SYNC_REFRESH_LOCAL,
 404         content::Source<Profile>(profile_),
 405         content::Details<const syncer::ModelTypeSet>(&types));
 406   }
 407
 408   if (local_tab_pool_out_of_sync_) {
 409     // If our tab pool is corrupt, pay the price of a full re-association to
 410     // fix things up.  This takes care of the new tab modification as well.
 411     RebuildAssociations();
 412     DCHECK(!local_tab_pool_out_of_sync_);
 413     return;
 414   }
 415
 416   syncer::SyncChangeList changes;
 417   // Associate tabs first so the synced session tracker is aware of them.
 418   AssociateTab(modified_tab, &changes);
 419   // Note, we always associate windows because it's possible a tab became
 420   // "interesting" by going to a valid URL, in which case it needs to be added
 421   // to the window's tab information.
 422   AssociateWindows(DONT_RELOAD_TABS, syncer::SyncDataList(), &changes);
 423   sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
 424 }
 425
 426 void SessionsSyncManager::OnFaviconsChanged(
 427     const std::set<GURL>& page_urls,
 428     const GURL& /* icon_url */) {
 429   // TODO(zea): consider a separate container for tabs with outstanding favicon
 430   // loads so we don't have to iterate through all tabs comparing urls.
 431   for (const GURL& page_url : page_urls) {
 432     for (TabLinksMap::iterator tab_iter = local_tab_map_.begin();
 433          tab_iter != local_tab_map_.end();
 434          ++tab_iter) {
 435       if (tab_iter->second->url() == page_url)
 436         favicon_cache_.OnPageFaviconUpdated(page_url);
 437     }
 438   }
 439 }
 440
 441 void SessionsSyncManager::StopSyncing(syncer::ModelType type) {
 442   local_event_router_->Stop();
 443   sync_processor_.reset(NULL);
 444   error_handler_.reset();
 445   session_tracker_.Clear();
 446   local_tab_map_.clear();
 447   local_tab_pool_.Clear();
 448   current_machine_tag_.clear();
 449   current_session_name_.clear();
 450   local_session_header_node_id_ = TabNodePool::kInvalidTabNodeID;
 451 }
 452
 453 syncer::SyncDataList SessionsSyncManager::GetAllSyncData(
 454     syncer::ModelType type) const {
 455   syncer::SyncDataList list;
 456   const sync_driver::SyncedSession* session = NULL;
 457   if (!session_tracker_.LookupLocalSession(&session))
 458     return syncer::SyncDataList();
 459
 460   // First construct the header node.
 461   sync_pb::EntitySpecifics header_entity;
 462   header_entity.mutable_session()->set_session_tag(current_machine_tag());
 463   sync_pb::SessionHeader* header_specifics =
 464       header_entity.mutable_session()->mutable_header();
 465   header_specifics->MergeFrom(session->ToSessionHeader());
 466   syncer::SyncData data = syncer::SyncData::CreateLocalData(
 467         current_machine_tag(), current_session_name_, header_entity);
 468   list.push_back(data);
 469
 470   sync_driver::SyncedSession::SyncedWindowMap::const_iterator win_iter;
 471   for (win_iter = session->windows.begin();
 472        win_iter != session->windows.end(); ++win_iter) {
 473     std::vector<sessions::SessionTab*>::const_iterator tabs_iter;
 474     for (tabs_iter = win_iter->second->tabs.begin();
 475          tabs_iter != win_iter->second->tabs.end(); ++tabs_iter) {
 476       sync_pb::EntitySpecifics entity;
 477       sync_pb::SessionSpecifics* specifics = entity.mutable_session();
 478       specifics->mutable_tab()->MergeFrom((*tabs_iter)->ToSyncData());
 479       specifics->set_session_tag(current_machine_tag_);
 480
 481       TabLinksMap::const_iterator tab_map_iter = local_tab_map_.find(
 482           (*tabs_iter)->tab_id.id());
 483       DCHECK(tab_map_iter != local_tab_map_.end());
 484       specifics->set_tab_node_id(tab_map_iter->second->tab_node_id());
 485       syncer::SyncData data = syncer::SyncData::CreateLocalData(
 486           TabNodePool::TabIdToTag(current_machine_tag_,
 487                                    specifics->tab_node_id()),
 488           current_session_name_,
 489           entity);
 490       list.push_back(data);
 491     }
 492   }
 493   return list;
 494 }
 495
 496 bool SessionsSyncManager::GetLocalSession(
 497     const sync_driver::SyncedSession** local_session) {
 498   if (current_machine_tag_.empty())
 499     return false;
 500   *local_session = session_tracker_.GetSession(current_machine_tag());
 501   return true;
 502 }
 503
 504 syncer::SyncError SessionsSyncManager::ProcessSyncChanges(
 505     const tracked_objects::Location& from_here,
 506     const syncer::SyncChangeList& change_list) {
 507   if (!sync_processor_.get()) {
 508     syncer::SyncError error(FROM_HERE,
 509                             syncer::SyncError::DATATYPE_ERROR,
 510                             "Models not yet associated.",
 511                             syncer::SESSIONS);
 512     return error;
 513   }
 514
 515   for (syncer::SyncChangeList::const_iterator it = change_list.begin();
 516        it != change_list.end(); ++it) {
 517     DCHECK(it->IsValid());
 518     DCHECK(it->sync_data().GetSpecifics().has_session());
 519     const sync_pb::SessionSpecifics& session =
 520         it->sync_data().GetSpecifics().session();
 521     switch (it->change_type()) {
 522       case syncer::SyncChange::ACTION_DELETE:
 523         // Deletions are all or nothing (since we only ever delete entire
 524         // sessions). Therefore we don't care if it's a tab node or meta node,
 525         // and just ensure we've disassociated.
 526         if (current_machine_tag() == session.session_tag()) {
 527           // Another client has attempted to delete our local data (possibly by
 528           // error or a clock is inaccurate). Just ignore the deletion for now
 529           // to avoid any possible ping-pong delete/reassociate sequence, but
 530           // remember that this happened as our TabNodePool is inconsistent.
 531           local_tab_pool_out_of_sync_ = true;
 532           LOG(WARNING) << "Local session data deleted. Ignoring until next "
 533                        << "local navigation event.";
 534         } else if (session.has_header()) {
 535           // Disassociate only when header node is deleted. For tab node
 536           // deletions, the header node will be updated and foreign tab will
 537           // get deleted.
 538           DisassociateForeignSession(session.session_tag());
 539         }
 540         continue;
 541       case syncer::SyncChange::ACTION_ADD:
 542       case syncer::SyncChange::ACTION_UPDATE:
 543         if (current_machine_tag() == session.session_tag()) {
 544           // We should only ever receive a change to our own machine's session
 545           // info if encryption was turned on. In that case, the data is still
 546           // the same, so we can ignore.
 547           LOG(WARNING) << "Dropping modification to local session.";
 548           return syncer::SyncError();
 549         }
 550         UpdateTrackerWithForeignSession(
 551             session, syncer::SyncDataRemote(it->sync_data()).GetModifiedTime());
 552         break;
 553       default:
 554         NOTREACHED() << "Processing sync changes failed, unknown change type.";
 555     }
 556   }
 557
 558   content::NotificationService::current()->Notify(
 559       chrome::NOTIFICATION_FOREIGN_SESSION_UPDATED,
 560       content::Source<Profile>(profile_),
 561       content::NotificationService::NoDetails());
 562   return syncer::SyncError();
 563 }
 564
 565 syncer::SyncChange SessionsSyncManager::TombstoneTab(
 566     const sync_pb::SessionSpecifics& tab) {
 567   if (!tab.has_tab_node_id()) {
 568     LOG(WARNING) << "Old sessions node without tab node id; can't tombstone.";
 569     return syncer::SyncChange();
 570   } else {
 571     return syncer::SyncChange(
 572         FROM_HERE,
 573         SyncChange::ACTION_DELETE,
 574         SyncData::CreateLocalDelete(
 575             TabNodePool::TabIdToTag(current_machine_tag(),
 576                                      tab.tab_node_id()),
 577             syncer::SESSIONS));
 578   }
 579 }
 580
 581 bool SessionsSyncManager::GetAllForeignSessions(
 582     std::vector<const sync_driver::SyncedSession*>* sessions) {
 583   if (!session_tracker_.LookupAllForeignSessions(sessions))
 584     return false;
 585   std::sort(sessions->begin(), sessions->end(), SessionsRecencyComparator);
 586   return true;
 587 }
 588
 589 bool SessionsSyncManager::InitFromSyncModel(
 590     const syncer::SyncDataList& sync_data,
 591     syncer::SyncDataList* restored_tabs,
 592     syncer::SyncChangeList* new_changes) {
 593   bool found_current_header = false;
 594   for (syncer::SyncDataList::const_iterator it = sync_data.begin();
 595        it != sync_data.end();
 596        ++it) {
 597     const syncer::SyncData& data = *it;
 598     DCHECK(data.GetSpecifics().has_session());
 599     const sync_pb::SessionSpecifics& specifics = data.GetSpecifics().session();
 600     if (specifics.session_tag().empty() ||
 601            (specifics.has_tab() && (!specifics.has_tab_node_id() ||
 602                                     !specifics.tab().has_tab_id()))) {
 603       syncer::SyncChange tombstone(TombstoneTab(specifics));
 604       if (tombstone.IsValid())
 605         new_changes->push_back(tombstone);
 606     } else if (specifics.session_tag() != current_machine_tag()) {
 607       UpdateTrackerWithForeignSession(
 608           specifics, syncer::SyncDataRemote(data).GetModifiedTime());
 609     } else {
 610       // This is previously stored local session information.
 611       if (specifics.has_header() && !found_current_header) {
 612         // This is our previous header node, reuse it.
 613         found_current_header = true;
 614         if (specifics.header().has_client_name())
 615           current_session_name_ = specifics.header().client_name();
 616       } else {
 617         if (specifics.has_header() || !specifics.has_tab()) {
 618           LOG(WARNING) << "Found more than one session header node with local "
 619                        << "tag.";
 620           syncer::SyncChange tombstone(TombstoneTab(specifics));
 621           if (tombstone.IsValid())
 622             new_changes->push_back(tombstone);
 623         } else {
 624           // This is a valid old tab node, add it to the pool so it can be
 625           // reused for reassociation.
 626           local_tab_pool_.AddTabNode(specifics.tab_node_id());
 627           restored_tabs->push_back(*it);
 628         }
 629       }
 630     }
 631   }
 632   return found_current_header;
 633 }
 634
 635 void SessionsSyncManager::UpdateTrackerWithForeignSession(
 636     const sync_pb::SessionSpecifics& specifics,
 637     const base::Time& modification_time) {
 638   std::string foreign_session_tag = specifics.session_tag();
 639   DCHECK_NE(foreign_session_tag, current_machine_tag());
 640
 641   sync_driver::SyncedSession* foreign_session =
 642       session_tracker_.GetSession(foreign_session_tag);
 643   if (specifics.has_header()) {
 644     // Read in the header data for this foreign session.
 645     // Header data contains window information and ordered tab id's for each
 646     // window.
 647
 648     if (!IsValidSessionHeader(specifics.header())) {
 649       LOG(WARNING) << "Ignoring foreign session node with invalid header "
 650                    << "and tag " << foreign_session_tag << ".";
 651       return;
 652     }
 653
 654     // Load (or create) the SyncedSession object for this client.
 655     const sync_pb::SessionHeader& header = specifics.header();
 656     PopulateSessionHeaderFromSpecifics(header,
 657                                        modification_time,
 658                                        foreign_session);
 659
 660     // Reset the tab/window tracking for this session (must do this before
 661     // we start calling PutWindowInSession and PutTabInWindow so that all
 662     // unused tabs/windows get cleared by the CleanupSession(...) call).
 663     session_tracker_.ResetSessionTracking(foreign_session_tag);
 664
 665     // Process all the windows and their tab information.
 666     int num_windows = header.window_size();
 667     DVLOG(1) << "Associating " << foreign_session_tag << " with "
 668              << num_windows << " windows.";
 669
 670     for (int i = 0; i < num_windows; ++i) {
 671       const sync_pb::SessionWindow& window_s = header.window(i);
 672       SessionID::id_type window_id = window_s.window_id();
 673       session_tracker_.PutWindowInSession(foreign_session_tag,
 674                                           window_id);
 675       BuildSyncedSessionFromSpecifics(foreign_session_tag,
 676                                       window_s,
 677                                       modification_time,
 678                                       foreign_session->windows[window_id]);
 679     }
 680     // Delete any closed windows and unused tabs as necessary.
 681     session_tracker_.CleanupSession(foreign_session_tag);
 682   } else if (specifics.has_tab()) {
 683     const sync_pb::SessionTab& tab_s = specifics.tab();
 684     SessionID::id_type tab_id = tab_s.tab_id();
 685
 686     const sessions::SessionTab* existing_tab;
 687     if (session_tracker_.LookupSessionTab(
 688             foreign_session_tag, tab_id, &existing_tab) &&
 689         existing_tab->timestamp > modification_time) {
 690       DVLOG(1) << "Ignoring " << foreign_session_tag << "'s session tab "
 691                << tab_id << " with earlier modification time";
 692       return;
 693     }
 694
 695     sessions::SessionTab* tab =
 696         session_tracker_.GetTab(foreign_session_tag,
 697                                 tab_id,
 698                                 specifics.tab_node_id());
 699
 700     // Update SessionTab based on protobuf.
 701     tab->SetFromSyncData(tab_s, modification_time);
 702
 703     // If a favicon or favicon urls are present, load the URLs and visit
 704     // times into the in-memory favicon cache.
 705     RefreshFaviconVisitTimesFromForeignTab(tab_s, modification_time);
 706
 707     // Update the last modified time.
 708     if (foreign_session->modified_time < modification_time)
 709       foreign_session->modified_time = modification_time;
 710   } else {
 711     LOG(WARNING) << "Ignoring foreign session node with missing header/tab "
 712                  << "fields and tag " << foreign_session_tag << ".";
 713   }
 714 }
 715
 716 void SessionsSyncManager::InitializeCurrentMachineTag() {
 717   DCHECK(current_machine_tag_.empty());
 718   std::string persisted_guid;
 719   persisted_guid = sync_prefs_.GetSyncSessionsGUID();
 720   if (!persisted_guid.empty()) {
 721     current_machine_tag_ = persisted_guid;
 722     DVLOG(1) << "Restoring persisted session sync guid: " << persisted_guid;
 723   } else {
 724     DCHECK(local_device_);
 725     std::string cache_guid = local_device_->GetLocalSyncCacheGUID();
 726     DCHECK(!cache_guid.empty());
 727     current_machine_tag_ = BuildMachineTag(cache_guid);
 728     DVLOG(1) << "Creating session sync guid: " << current_machine_tag_;
 729     sync_prefs_.SetSyncSessionsGUID(current_machine_tag_);
 730   }
 731
 732   local_tab_pool_.SetMachineTag(current_machine_tag_);
 733 }
 734
 735 // static
 736 void SessionsSyncManager::PopulateSessionHeaderFromSpecifics(
 737     const sync_pb::SessionHeader& header_specifics,
 738     base::Time mtime,
 739     sync_driver::SyncedSession* session_header) {
 740   if (header_specifics.has_client_name())
 741     session_header->session_name = header_specifics.client_name();
 742   if (header_specifics.has_device_type()) {
 743     switch (header_specifics.device_type()) {
 744       case sync_pb::SyncEnums_DeviceType_TYPE_WIN:
 745         session_header->device_type = sync_driver::SyncedSession::TYPE_WIN;
 746         break;
 747       case sync_pb::SyncEnums_DeviceType_TYPE_MAC:
 748         session_header->device_type = sync_driver::SyncedSession::TYPE_MACOSX;
 749         break;
 750       case sync_pb::SyncEnums_DeviceType_TYPE_LINUX:
 751         session_header->device_type = sync_driver::SyncedSession::TYPE_LINUX;
 752         break;
 753       case sync_pb::SyncEnums_DeviceType_TYPE_CROS:
 754         session_header->device_type = sync_driver::SyncedSession::TYPE_CHROMEOS;
 755         break;
 756       case sync_pb::SyncEnums_DeviceType_TYPE_PHONE:
 757         session_header->device_type = sync_driver::SyncedSession::TYPE_PHONE;
 758         break;
 759       case sync_pb::SyncEnums_DeviceType_TYPE_TABLET:
 760         session_header->device_type = sync_driver::SyncedSession::TYPE_TABLET;
 761         break;
 762       case sync_pb::SyncEnums_DeviceType_TYPE_OTHER:
 763         // Intentionally fall-through
 764       default:
 765         session_header->device_type = sync_driver::SyncedSession::TYPE_OTHER;
 766         break;
 767     }
 768   }
 769   session_header->modified_time = mtime;
 770 }
 771
 772 // static
 773 void SessionsSyncManager::BuildSyncedSessionFromSpecifics(
 774     const std::string& session_tag,
 775     const sync_pb::SessionWindow& specifics,
 776     base::Time mtime,
 777     sessions::SessionWindow* session_window) {
 778   if (specifics.has_window_id())
 779     session_window->window_id.set_id(specifics.window_id());
 780   if (specifics.has_selected_tab_index())
 781     session_window->selected_tab_index = specifics.selected_tab_index();
 782   if (specifics.has_browser_type()) {
 783     // TODO(skuhne): Sync data writes |BrowserType| not
 784     // |SessionWindow::WindowType|. This should get changed.
 785     if (specifics.browser_type() ==
 786         sync_pb::SessionWindow_BrowserType_TYPE_TABBED) {
 787       session_window->type = sessions::SessionWindow::TYPE_TABBED;
 788     } else {
 789       session_window->type = sessions::SessionWindow::TYPE_POPUP;
 790     }
 791   }
 792   session_window->timestamp = mtime;
 793   session_window->tabs.resize(specifics.tab_size(), NULL);
 794   for (int i = 0; i < specifics.tab_size(); i++) {
 795     SessionID::id_type tab_id = specifics.tab(i);
 796     session_tracker_.PutTabInWindow(session_tag,
 797                                     session_window->window_id.id(),
 798                                     tab_id,
 799                                     i);
 800   }
 801 }
 802
 803 void SessionsSyncManager::RefreshFaviconVisitTimesFromForeignTab(
 804     const sync_pb::SessionTab& tab, const base::Time& modification_time) {
 805   // First go through and iterate over all the navigations, checking if any
 806   // have valid favicon urls.
 807   for (int i = 0; i < tab.navigation_size(); ++i) {
 808     if (!tab.navigation(i).favicon_url().empty()) {
 809       const std::string& page_url = tab.navigation(i).virtual_url();
 810       const std::string& favicon_url = tab.navigation(i).favicon_url();
 811       favicon_cache_.OnReceivedSyncFavicon(GURL(page_url),
 812                                            GURL(favicon_url),
 813                                            std::string(),
 814                                            syncer::TimeToProtoTime(
 815                                                modification_time));
 816     }
 817   }
 818 }
 819
 820 bool SessionsSyncManager::GetSyncedFaviconForPageURL(
 821     const std::string& page_url,
 822     scoped_refptr<base::RefCountedMemory>* favicon_png) const {
 823   return favicon_cache_.GetSyncedFaviconForPageURL(GURL(page_url), favicon_png);
 824 }
 825
 826 void SessionsSyncManager::DeleteForeignSession(const std::string& tag) {
 827   syncer::SyncChangeList changes;
 828   DeleteForeignSessionInternal(tag, &changes);
 829   sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
 830 }
 831
 832 void SessionsSyncManager::DeleteForeignSessionInternal(
 833     const std::string& tag, syncer::SyncChangeList* change_output) {
 834   if (tag == current_machine_tag()) {
 835     LOG(ERROR) << "Attempting to delete local session. This is not currently "
 836                << "supported.";
 837     return;
 838   }
 839
 840   std::set<int> tab_node_ids_to_delete;
 841   session_tracker_.LookupTabNodeIds(tag, &tab_node_ids_to_delete);
 842   if (!DisassociateForeignSession(tag)) {
 843     // We don't have any data for this session, our work here is done!
 844     return;
 845   }
 846
 847   // Prepare deletes for the meta-node as well as individual tab nodes.
 848   change_output->push_back(syncer::SyncChange(
 849       FROM_HERE,
 850       SyncChange::ACTION_DELETE,
 851       SyncData::CreateLocalDelete(tag, syncer::SESSIONS)));
 852
 853   for (std::set<int>::const_iterator it = tab_node_ids_to_delete.begin();
 854        it != tab_node_ids_to_delete.end();
 855        ++it) {
 856     change_output->push_back(syncer::SyncChange(
 857         FROM_HERE,
 858         SyncChange::ACTION_DELETE,
 859         SyncData::CreateLocalDelete(TabNodePool::TabIdToTag(tag, *it),
 860                                     syncer::SESSIONS)));
 861   }
 862   content::NotificationService::current()->Notify(
 863       chrome::NOTIFICATION_FOREIGN_SESSION_UPDATED,
 864       content::Source<Profile>(profile_),
 865       content::NotificationService::NoDetails());
 866 }
 867
 868 bool SessionsSyncManager::DisassociateForeignSession(
 869     const std::string& foreign_session_tag) {
 870   if (foreign_session_tag == current_machine_tag()) {
 871     DVLOG(1) << "Local session deleted! Doing nothing until a navigation is "
 872              << "triggered.";
 873     return false;
 874   }
 875   DVLOG(1) << "Disassociating session " << foreign_session_tag;
 876   return session_tracker_.DeleteSession(foreign_session_tag);
 877 }
 878
 879 // static
 880 GURL SessionsSyncManager::GetCurrentVirtualURL(
 881     const SyncedTabDelegate& tab_delegate) {
 882   const NavigationEntry* current_entry =
 883       tab_delegate.GetCurrentEntryMaybePending();
 884   return current_entry->GetVirtualURL();
 885 }
 886
 887 // static
 888 GURL SessionsSyncManager::GetCurrentFaviconURL(
 889     const SyncedTabDelegate& tab_delegate) {
 890   const NavigationEntry* current_entry =
 891       tab_delegate.GetCurrentEntryMaybePending();
 892   return (current_entry->GetFavicon().valid ?
 893           current_entry->GetFavicon().url :
 894           GURL());
 895 }
 896
 897 bool SessionsSyncManager::GetForeignSession(
 898     const std::string& tag,
 899     std::vector<const sessions::SessionWindow*>* windows) {
 900   return session_tracker_.LookupSessionWindows(tag, windows);
 901 }
 902
 903 bool SessionsSyncManager::GetForeignSessionTabs(
 904     const std::string& tag,
 905     std::vector<const sessions::SessionTab*>* tabs) {
 906   std::vector<const sessions::SessionWindow*> windows;
 907   if (!session_tracker_.LookupSessionWindows(tag, &windows))
 908     return false;
 909
 910   // Prune those tabs that are not syncable or are NewTabPage, then sort them
 911   // from most recent to least recent, independent of which window the tabs were
 912   // from.
 913   for (size_t j = 0; j < windows.size(); ++j) {
 914     const sessions::SessionWindow* window = windows[j];
 915     for (size_t t = 0; t < window->tabs.size(); ++t) {
 916       sessions::SessionTab* const tab = window->tabs[t];
 917       if (tab->navigations.empty())
 918         continue;
 919       const sessions::SerializedNavigationEntry& current_navigation =
 920           tab->navigations.at(tab->normalized_navigation_index());
 921       if (search::IsNTPURL(current_navigation.virtual_url(), profile_)) {
 922         continue;
 923       }
 924       tabs->push_back(tab);
 925     }
 926   }
 927   std::sort(tabs->begin(), tabs->end(), TabsRecencyComparator);
 928   return true;
 929 }
 930
 931 bool SessionsSyncManager::GetForeignTab(
 932     const std::string& tag,
 933     const SessionID::id_type tab_id,
 934     const sessions::SessionTab** tab) {
 935   const sessions::SessionTab* synced_tab = NULL;
 936   bool success = session_tracker_.LookupSessionTab(tag,
 937                                                    tab_id,
 938                                                    &synced_tab);
 939   if (success)
 940     *tab = synced_tab;
 941   return success;
 942 }
 943
 944 void SessionsSyncManager::LocalTabDelegateToSpecifics(
 945     const SyncedTabDelegate& tab_delegate,
 946     sync_pb::SessionSpecifics* specifics) {
 947   sessions::SessionTab* session_tab = NULL;
 948   session_tab =
 949       session_tracker_.GetTab(current_machine_tag(),
 950                               tab_delegate.GetSessionId(),
 951                               tab_delegate.GetSyncId());
 952   SetSessionTabFromDelegate(tab_delegate, base::Time::Now(), session_tab);
 953   SetVariationIds(session_tab);
 954   sync_pb::SessionTab tab_s = session_tab->ToSyncData();
 955   specifics->set_session_tag(current_machine_tag_);
 956   specifics->set_tab_node_id(tab_delegate.GetSyncId());
 957   specifics->mutable_tab()->CopyFrom(tab_s);
 958 }
 959
 960 void SessionsSyncManager::AssociateRestoredPlaceholderTab(
 961     const SyncedTabDelegate& tab_delegate,
 962     SessionID::id_type new_tab_id,
 963     const syncer::SyncDataList& restored_tabs,
 964     syncer::SyncChangeList* change_output) {
 965   DCHECK_NE(tab_delegate.GetSyncId(), TabNodePool::kInvalidTabNodeID);
 966   // Rewrite the tab using |restored_tabs| to retrieve the specifics.
 967   if (restored_tabs.empty()) {
 968     DLOG(WARNING) << "Can't Update tab ID.";
 969     return;
 970   }
 971
 972   for (syncer::SyncDataList::const_iterator it = restored_tabs.begin();
 973        it != restored_tabs.end();
 974        ++it) {
 975     if (it->GetSpecifics().session().tab_node_id() !=
 976         tab_delegate.GetSyncId()) {
 977       continue;
 978     }
 979
 980     sync_pb::EntitySpecifics entity;
 981     sync_pb::SessionSpecifics* specifics = entity.mutable_session();
 982     specifics->CopyFrom(it->GetSpecifics().session());
 983     DCHECK(specifics->has_tab());
 984
 985     // Update tab node pool with the new association.
 986     local_tab_pool_.ReassociateTabNode(tab_delegate.GetSyncId(),
 987                                        new_tab_id);
 988     TabLink* tab_link = new TabLink(tab_delegate.GetSyncId(),
 989                                     &tab_delegate);
 990     local_tab_map_[new_tab_id] = make_linked_ptr<TabLink>(tab_link);
 991
 992     if (specifics->tab().tab_id() == new_tab_id)
 993       return;
 994
 995     // The tab_id changed (e.g due to session restore), so update sync.
 996     specifics->mutable_tab()->set_tab_id(new_tab_id);
 997     syncer::SyncData data = syncer::SyncData::CreateLocalData(
 998         TabNodePool::TabIdToTag(current_machine_tag_,
 999                                  specifics->tab_node_id()),
1000         current_session_name_,
1001         entity);
1002     change_output->push_back(syncer::SyncChange(
1003         FROM_HERE, syncer::SyncChange::ACTION_UPDATE, data));
1004     return;
1005   }
1006 }
1007
1008 // static
1009 void SessionsSyncManager::SetSessionTabFromDelegate(
1010       const SyncedTabDelegate& tab_delegate,
1011       base::Time mtime,
1012       sessions::SessionTab* session_tab) {
1013   DCHECK(session_tab);
1014   session_tab->window_id.set_id(tab_delegate.GetWindowId());
1015   session_tab->tab_id.set_id(tab_delegate.GetSessionId());
1016   session_tab->tab_visual_index = 0;
1017   // Use -1 to indicate that the index hasn't been set properly yet.
1018   session_tab->current_navigation_index = -1;
1019   session_tab->pinned = tab_delegate.IsPinned();
1020   session_tab->extension_app_id = tab_delegate.GetExtensionAppId();
1021   session_tab->user_agent_override.clear();
1022   session_tab->timestamp = mtime;
1023   const int current_index = tab_delegate.GetCurrentEntryIndex();
1024   const int min_index = std::max(0, current_index - kMaxSyncNavigationCount);
1025   const int max_index = std::min(current_index + kMaxSyncNavigationCount,
1026                                  tab_delegate.GetEntryCount());
1027   bool is_supervised = tab_delegate.ProfileIsSupervised();
1028   session_tab->navigations.clear();
1029
1030   for (int i = min_index; i < max_index; ++i) {
1031     const NavigationEntry* entry = tab_delegate.GetEntryAtIndexMaybePending(i);
1032     DCHECK(entry);
1033     if (!entry->GetVirtualURL().is_valid())
1034       continue;
1035
1036     // Set current_navigation_index to the index in navigations.
1037     if (i == current_index)
1038       session_tab->current_navigation_index = session_tab->navigations.size();
1039
1040     session_tab->navigations.push_back(
1041         ContentSerializedNavigationBuilder::FromNavigationEntry(i, *entry));
1042     if (is_supervised) {
1043       session_tab->navigations.back().set_blocked_state(
1044           SerializedNavigationEntry::STATE_ALLOWED);
1045     }
1046   }
1047
1048   // If the current navigation is invalid, set the index to the end of the
1049   // navigation array.
1050   if (session_tab->current_navigation_index < 0) {
1051     session_tab->current_navigation_index =
1052         session_tab->navigations.size() - 1;
1053   }
1054
1055   if (is_supervised) {
1056     const std::vector<const NavigationEntry*>& blocked_navigations =
1057         *tab_delegate.GetBlockedNavigations();
1058     int offset = session_tab->navigations.size();
1059     for (size_t i = 0; i < blocked_navigations.size(); ++i) {
1060       session_tab->navigations.push_back(
1061           ContentSerializedNavigationBuilder::FromNavigationEntry(
1062               i + offset, *blocked_navigations[i]));
1063       session_tab->navigations.back().set_blocked_state(
1064           SerializedNavigationEntry::STATE_BLOCKED);
1065       // TODO(bauerb): Add categories
1066     }
1067   }
1068   session_tab->session_storage_persistent_id.clear();
1069 }
1070
1071 // static
1072 void SessionsSyncManager::SetVariationIds(sessions::SessionTab* session_tab) {
1073   base::FieldTrial::ActiveGroups active_groups;
1074   base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
1075   for (const base::FieldTrial::ActiveGroup& group : active_groups) {
1076     const variations::VariationID id =
1077         variations::GetGoogleVariationID(variations::CHROME_SYNC_SERVICE,
1078                                          group.trial_name, group.group_name);
1079     if (id != variations::EMPTY_ID)
1080       session_tab->variation_ids.push_back(id);
1081   }
1082 }
1083
1084 FaviconCache* SessionsSyncManager::GetFaviconCache() {
1085   return &favicon_cache_;
1086 }
1087
1088 SyncedWindowDelegatesGetter*
1089 SessionsSyncManager::GetSyncedWindowDelegatesGetter() const {
1090   return synced_window_getter_.get();
1091 }
1092
1093 void SessionsSyncManager::DoGarbageCollection() {
1094   std::vector<const sync_driver::SyncedSession*> sessions;
1095   if (!GetAllForeignSessions(&sessions))
1096     return;  // No foreign sessions.
1097
1098   // Iterate through all the sessions and delete any with age older than
1099   // |stale_session_threshold_days_|.
1100   syncer::SyncChangeList changes;
1101   for (std::vector<const sync_driver::SyncedSession*>::const_iterator iter =
1102            sessions.begin();
1103        iter != sessions.end(); ++iter) {
1104     const sync_driver::SyncedSession* session = *iter;
1105     int session_age_in_days =
1106         (base::Time::Now() - session->modified_time).InDays();
1107     std::string session_tag = session->session_tag;
1108     if (session_age_in_days > 0 &&  // If false, local clock is not trustworty.
1109         static_cast<size_t>(session_age_in_days) >
1110             stale_session_threshold_days_) {
1111       DVLOG(1) << "Found stale session " << session_tag
1112                << " with age " << session_age_in_days << ", deleting.";
1113       DeleteForeignSessionInternal(session_tag, &changes);
1114     }
1115   }
1116
1117   if (!changes.empty())
1118     sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
1119 }
1120
1121 };  // namespace browser_sync