[Sync] Refactor sync configuration logic.

chrome/browser/sync/glue/sync_backend_host.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 "build/build_config.h"
 
 #include "chrome/browser/sync/glue/sync_backend_host.h"
 
 #include <algorithm>
 #include <map>
@@ skipping 113 matching lines @@
   // Called when the user disables or enables a sync type.
   void DoUpdateEnabledTypes(const syncable::ModelTypeSet& enabled_types);
 
   // Called to tell the syncapi to start syncing (generally after
   // initialization and authentication).
   void DoStartSyncing(const ModelSafeRoutingInfo& routing_info);
 
   // Called to clear server data.
   void DoRequestClearServerData();
 
-  // Called to cleanup disabled types.
-  void DoRequestCleanupDisabledTypes(
-      const browser_sync::ModelSafeRoutingInfo& routing_info);
-
   // Called to set the passphrase for encryption.
   void DoSetEncryptionPassphrase(const std::string& passphrase,
                                  bool is_explicit);
 
   // Called to decrypt the pending keys.
   void DoSetDecryptionPassphrase(const std::string& passphrase);
 
   // Called to turn on encryption of all sync data as well as
   // reencrypt everything.
   void DoEnableEncryptEverything();
 
   // Called to refresh encryption with the most recent passphrase
   // and set of encrypted types. Also adds device information to the nigori
   // node. |done_callback| is called on the sync thread.
   void DoRefreshNigori(const base::Closure& done_callback);
 
   // The shutdown order is a bit complicated:
   // 1) From |sync_thread_|, invoke the syncapi Shutdown call to do
   //    a final SaveChanges, and close sqlite handles.
   // 2) Then, from |frontend_loop_|, halt the sync_thread_ (which is
   //    a blocking call). This causes syncapi thread-exit handlers
   //    to run and make use of cached pointers to various components
   //    owned implicitly by us.
   // 3) Destroy this Core. That will delete syncapi components in a
   //    safe order because the thread that was using them has exited
   //    (in step 2).
   void DoStopSyncManagerForShutdown(const base::Closure& closure);
   void DoShutdown(bool stopping_sync);
 
-  virtual void DoRequestConfig(
-      const browser_sync::ModelSafeRoutingInfo& routing_info,
+  // Configuration methods that must execute on sync loop.
+  void DoConfigureSyncer(
+      sync_api::ConfigureReason reason,
       syncable::ModelTypeSet types_to_config,
-      sync_api::ConfigureReason reason);
-
-  // Start the configuration mode.  |callback| is called on the sync
-  // thread.
-  virtual void DoStartConfiguration(const base::Closure& callback);
+      const browser_sync::ModelSafeRoutingInfo routing_info,
+      const base::Callback<void(syncable::ModelTypeSet)>& ready_task,
+      const base::Closure& retry_callback);
+  void DoFinishConfigureDataTypes(
+      syncable::ModelTypeSet types_to_config,
+      const base::Callback<void(syncable::ModelTypeSet)>& ready_task);
+  void DoRetryConfiguration(
+      const base::Closure& retry_callback);
 
   // Set the base request context to use when making HTTP calls.
   // This method will add a reference to the context to persist it
   // on the IO thread. Must be removed from IO thread.
 
   sync_api::SyncManager* sync_manager() { return sync_manager_.get(); }
 
   // Delete the sync data folder to cleanup backend data.  Happens the first
   // time sync is enabled for a user (to prevent accidentally reusing old
   // sync databases), as well as shutdown when you're no longer syncing.
   void DeleteSyncDataFolder();
 
-  // A callback from the SyncerThread when it is safe to continue config.
-  void FinishConfigureDataTypes();
-
  private:
   friend class base::RefCountedThreadSafe<SyncBackendHost::Core>;
   friend class SyncBackendHostForProfileSyncTest;
 
   virtual ~Core();
 
   // Invoked when initialization of syncapi is complete and we can start
   // our timer.
   // This must be called from the thread on which SaveChanges is intended to
   // be run on; the host's |sync_thread_|.
@@ skipping 349 matching lines @@
   base::TimeDelta stop_sync_thread_time = base::Time::Now() -
       stop_thread_start_time;
   UMA_HISTOGRAM_TIMES("Sync.Shutdown.StopSyncThreadTime",
                       stop_sync_thread_time);
 
   registrar_.reset();
   frontend_ = NULL;
   core_ = NULL;  // Releases reference to core_.
 }
 
+// TODO(sync): remove |disabled_types| completely, as it's just the set of
+// registered types - the set of desired types.
 void SyncBackendHost::ConfigureDataTypes(
     sync_api::ConfigureReason reason,
-    syncable::ModelTypeSet types_to_add,
-    syncable::ModelTypeSet types_to_remove,
+    const syncable::ModelTypeSet& desired_types,
+    const syncable::ModelTypeSet& disabled_types,
     NigoriState nigori_state,
-    base::Callback<void(syncable::ModelTypeSet)> ready_task,
-    base::Callback<void()> retry_callback) {
-  syncable::ModelTypeSet types_to_add_with_nigori = types_to_add;
-  syncable::ModelTypeSet types_to_remove_with_nigori = types_to_remove;
+    const base::Callback<void(syncable::ModelTypeSet)>& ready_task,
+    const base::Callback<void()>& retry_callback) {
+  syncable::ModelTypeSet desired_types_with_nigori = desired_types;
+  syncable::ModelTypeSet disabled_types_with_nigori = disabled_types;
   if (nigori_state == WITH_NIGORI) {
-    types_to_add_with_nigori.Put(syncable::NIGORI);
-    types_to_remove_with_nigori.Remove(syncable::NIGORI);
+    desired_types_with_nigori.Put(syncable::NIGORI);
+    disabled_types_with_nigori.Remove(syncable::NIGORI);
   } else {
-    types_to_add_with_nigori.Remove(syncable::NIGORI);
-    types_to_remove_with_nigori.Put(syncable::NIGORI);
+    desired_types_with_nigori.Remove(syncable::NIGORI);
+    disabled_types_with_nigori.Put(syncable::NIGORI);
   }
-  // Only one configure is allowed at a time.
-  DCHECK(!pending_config_mode_state_.get());
-  DCHECK(!pending_download_state_.get());
+  // Only one configure is allowed at a time (DataTypeManager handles user
+  // changes that happen while the syncer is reconfiguraing, and will only
+  // trigger another call to ConfigureDataTypes once the current reconfiguration
+  // completes).
   DCHECK_GT(initialization_state_, NOT_INITIALIZED);
 
-  pending_config_mode_state_.reset(new PendingConfigureDataTypesState());
-  pending_config_mode_state_->ready_task = ready_task;
-  pending_config_mode_state_->types_to_add = types_to_add_with_nigori;
-  pending_config_mode_state_->added_types =
-      registrar_->ConfigureDataTypes(types_to_add_with_nigori,
-                                     types_to_remove_with_nigori);
-  pending_config_mode_state_->reason = reason;
-  pending_config_mode_state_->retry_callback = retry_callback;
+  // enabled_types \setunion disabled_types gives the set of all registered
+  // types (i.e. types with datatype controllers registered).
+  ModelSafeRoutingInfo routing_info;
+  registrar_->ConfigureDataTypes(desired_types_with_nigori,
+                                 disabled_types_with_nigori);
+  registrar_->GetModelSafeRoutingInfo(&routing_info);
 
-  // Cleanup disabled types before starting configuration so that
-  // callers can assume that the data types are cleaned up once
-  // configuration is done.
-  if (!types_to_remove_with_nigori.Empty()) {
-    ModelSafeRoutingInfo routing_info;
-    registrar_->GetModelSafeRoutingInfo(&routing_info);
-    sync_thread_.message_loop()->PostTask(
-        FROM_HERE,
-        base::Bind(&SyncBackendHost::Core::DoRequestCleanupDisabledTypes,
-                   core_.get(),
-                   routing_info));
-  }
+  // |enabled_types| is desired_types_with_nigori \setintersect types with
+  // model safe workers (e.g. the password store may fail to start up, in which
+  // case we have no model safe worker for it and should not enable it).
+  // TODO(sync): This shouldn't be necessary. We should do whatever filtering
+  // we need beforehand as part of ProfileSyncComponentsFactory's
+  // RegisterDataTypes.
+  const syncable::ModelTypeSet enabled_types =
+      GetRoutingInfoTypes(routing_info);
 
-  StartConfiguration(
-      base::Bind(&SyncBackendHost::Core::FinishConfigureDataTypes,
-                 core_.get()));
-}
+  // Figure out which types need to actually be downloaded. We pass those on
+  // to the syncer while it's in configuration mode so that they can be
+  // downloaded before we perform association. Once we switch to normal mode
+  // downloads will get applied normally and hit the datatype's change
+  // processor.
+  // A datatype is in need of downloading if any of the following are true:
+  // 1. it's enabled and initial_sync_ended is false (initial_sync_ended is
+  //    set after applying updates, and hence is a more conservative measure
+  //    than having a non-empty progress marker, which is set during
+  //    StoreTimestamps).
+  // 2. the type is NIGORI, and any other datatype is being downloaded (nigori
+  //    is always included if we download a datatype).
+  // TODO(sync): consider moving this logic onto the sync thread (perhaps
+  // as part of SyncManager::ConfigureSyncer).
+  syncable::ModelTypeSet initial_sync_ended_types =
+      core_->sync_manager()->InitialSyncEndedTypes();
+  initial_sync_ended_types.RetainAll(enabled_types);
+  syncable::ModelTypeSet types_to_config =
+      Difference(enabled_types, initial_sync_ended_types);
+  if (!types_to_config.Empty() && enabled_types.Has(syncable::NIGORI))
+    types_to_config.Put(syncable::NIGORI);
 
-void SyncBackendHost::StartConfiguration(const base::Closure& callback) {
-  // Put syncer in the config mode. DTM will put us in normal mode once it is
-  // done. This is to ensure we dont do a normal sync when we are doing model
-  // association.
-  sync_thread_.message_loop()->PostTask(FROM_HERE, base::Bind(
-      &SyncBackendHost::Core::DoStartConfiguration, core_.get(), callback));
+  SDVLOG(1) << "Types "
+            << syncable::ModelTypeSetToString(types_to_config)
+            << " added; calling DoConfigureSyncer";
+  // TODO(zea): figure out how to bypass this call if no types are being
+  // configured and GetKey is not needed. For now we rely on determining the
+  // need for GetKey as part of the SyncManager::ConfigureSyncer logic.
+  RequestConfigureSyncer(reason,
+                         types_to_config,
+                         routing_info,
+                         ready_task,
+                         retry_callback);
 }
 
 void SyncBackendHost::EnableEncryptEverything() {
   sync_thread_.message_loop()->PostTask(FROM_HERE,
      base::Bind(&SyncBackendHost::Core::DoEnableEncryptEverything,
                 core_.get()));
 }
 
 void SyncBackendHost::ActivateDataType(
     syncable::ModelType type, ModelSafeGroup group,
@@ skipping 57 matching lines @@
   } else {
     NOTREACHED();
   }
 }
 
 void SyncBackendHost::InitCore(const DoInitializeOptions& options) {
   sync_thread_.message_loop()->PostTask(FROM_HERE,
       base::Bind(&SyncBackendHost::Core::DoInitialize, core_.get(), options));
 }
 
-void SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop(
-    const SyncSessionSnapshot& snapshot) {
-  if (!frontend_)
-    return;
-  DCHECK_EQ(MessageLoop::current(), frontend_loop_);
-
-  last_snapshot_ = snapshot;
-
-  SDVLOG(1) << "Got snapshot " << snapshot.ToString();
-
-  const syncable::ModelTypeSet to_migrate =
-      snapshot.syncer_status().types_needing_local_migration;
-  if (!to_migrate.Empty())
-    frontend_->OnMigrationNeededForTypes(to_migrate);
-
-  // Process any changes to the datatypes we're syncing.
-  // TODO(sync): add support for removing types.
-  if (initialized())
-    AddExperimentalTypes();
-
-  // If we are waiting for a configuration change, check here to see
-  // if this sync cycle has initialized all of the types we've been
-  // waiting for.
-  if (pending_download_state_.get()) {
-    const syncable::ModelTypeSet types_to_add =
-        pending_download_state_->types_to_add;
-    const syncable::ModelTypeSet added_types =
-        pending_download_state_->added_types;
-    DCHECK(types_to_add.HasAll(added_types));
-    const syncable::ModelTypeSet initial_sync_ended =
-        snapshot.initial_sync_ended();
-    const syncable::ModelTypeSet failed_configuration_types =
-        Difference(added_types, initial_sync_ended);
-    SDVLOG(1)
-        << "Added types: "
-        << syncable::ModelTypeSetToString(added_types)
-        << ", configured types: "
-        << syncable::ModelTypeSetToString(initial_sync_ended)
-        << ", failed configuration types: "
-        << syncable::ModelTypeSetToString(failed_configuration_types);
-
-    if (!failed_configuration_types.Empty() &&
-        snapshot.retry_scheduled()) {
-      // Inform the caller that download failed but we are retrying.
-      if (!pending_download_state_->retry_in_progress) {
-        pending_download_state_->retry_callback.Run();
-        pending_download_state_->retry_in_progress = true;
-      }
-      // Nothing more to do.
-      return;
-    }
-
-    scoped_ptr<PendingConfigureDataTypesState> state(
-        pending_download_state_.release());
-    state->ready_task.Run(failed_configuration_types);
-
-    // Syncer did not report an error but did not download everything
-    // we requested either. So abort. The caller of the config will cleanup.
-    if (!failed_configuration_types.Empty())
-      return;
-  }
-
-  if (initialized())
-    frontend_->OnSyncCycleCompleted();
+void SyncBackendHost::RequestConfigureSyncer(
+    sync_api::ConfigureReason reason,
+    syncable::ModelTypeSet types_to_config,
+    const browser_sync::ModelSafeRoutingInfo& routing_info,
+    const base::Callback<void(syncable::ModelTypeSet)>& ready_task,
+    const base::Closure& retry_callback) {
+  sync_thread_.message_loop()->PostTask(FROM_HERE,
+       base::Bind(&SyncBackendHost::Core::DoConfigureSyncer,
+                  core_.get(),
+                  reason,
+                  types_to_config,
+                  routing_info,
+                  ready_task,
+                  retry_callback));
 }
 
-void SyncBackendHost::FinishConfigureDataTypesOnFrontendLoop() {
-  DCHECK_EQ(MessageLoop::current(), frontend_loop_);
-  // Nudge the syncer. This is necessary for both datatype addition/deletion.
-  //
-  // Deletions need a nudge in order to ensure the deletion occurs in a timely
-  // manner (see issue 56416).
-  //
-  // In the case of additions, on the next sync cycle, the syncer should
-  // notice that the routing info has changed and start the process of
-  // downloading updates for newly added data types.  Once this is
-  // complete, the configure_state_.ready_task_ is run via an
-  // OnInitializationComplete notification.
-
-  SDVLOG(1) << "Syncer in config mode. SBH executing "
-            << "FinishConfigureDataTypesOnFrontendLoop";
-
-
-  ModelSafeRoutingInfo routing_info;
-  registrar_->GetModelSafeRoutingInfo(&routing_info);
-  const syncable::ModelTypeSet enabled_types =
-      GetRoutingInfoTypes(routing_info);
+void SyncBackendHost::FinishConfigureDataTypesOnFrontendLoop(
+    const syncable::ModelTypeSet& types_to_configure,
+    const syncable::ModelTypeSet& configured_types,
+    const base::Callback<void(syncable::ModelTypeSet)>& ready_task) {
+  const syncable::ModelTypeSet failed_configuration_types =
+      Difference(types_to_configure, configured_types);
+  SDVLOG(1)
+      << "Added types: "
+      << syncable::ModelTypeSetToString(types_to_configure)
+      << ", configured types: "
+      << syncable::ModelTypeSetToString(configured_types)
+      << ", failed configuration types: "
+      << syncable::ModelTypeSetToString(failed_configuration_types);
 
   // Update |chrome_sync_notification_bridge_|'s enabled types here as it has
   // to happen on the UI thread.
-  chrome_sync_notification_bridge_.UpdateEnabledTypes(enabled_types);
-
-  if (pending_config_mode_state_->added_types.Empty() &&
-      !core_->sync_manager()->InitialSyncEndedTypes().HasAll(enabled_types)) {
-
-    // TODO(tim): Log / UMA / count this somehow?
-    // Add only the types with empty progress markers. Note: it is possible
-    // that some types have their initial_sync_ended be false but with non
-    // empty progress marker. Which is ok as the rest of the changes would
-    // be downloaded on a regular nudge and initial_sync_ended should be set
-    // to true. However this is a very corner case. So it is not explicitly
-    // handled.
-    pending_config_mode_state_->added_types =
-        sync_api::GetTypesWithEmptyProgressMarkerToken(enabled_types,
-                                                       GetUserShare());
-  }
-
-  // If we've added types, we always want to request a nudge/config (even if
-  // the initial sync is ended), in case we could not decrypt the data.
-  if (pending_config_mode_state_->added_types.Empty()) {
-    SDVLOG(1) << "No new types added; calling ready_task directly";
-    // No new types - just notify the caller that the types are available.
-    const syncable::ModelTypeSet failed_configuration_types;
-    pending_config_mode_state_->ready_task.Run(failed_configuration_types);
-  } else {
-    pending_download_state_.reset(pending_config_mode_state_.release());
-
-    // Always configure nigori if it's enabled.
-    syncable::ModelTypeSet types_to_config =
-        pending_download_state_->added_types;
-    if (IsNigoriEnabled()) {
-      // Note: Nigori is the only type that gets added with a nonempty
-      // progress marker during config. If the server returns a migration
-      // error then we will go into unrecoverable error. We dont handle it
-      // explicitly because server might help us out here by not sending a
-      // migraiton error for nigori during config.
-      types_to_config.Put(syncable::NIGORI);
-    }
-    SDVLOG(1) << "Types "
-              << syncable::ModelTypeSetToString(types_to_config)
-              << " added; calling DoRequestConfig";
-    ModelSafeRoutingInfo routing_info;
-    registrar_->GetModelSafeRoutingInfo(&routing_info);
-    sync_thread_.message_loop()->PostTask(FROM_HERE,
-         base::Bind(&SyncBackendHost::Core::DoRequestConfig,
-                    core_.get(),
-                    routing_info,
-                    types_to_config,
-                    pending_download_state_->reason));
-  }
-
-  pending_config_mode_state_.reset();
+  chrome_sync_notification_bridge_.UpdateEnabledTypes(configured_types);
 
   // Notify SyncManager (especially the notification listener) about new types.
   sync_thread_.message_loop()->PostTask(FROM_HERE,
       base::Bind(&SyncBackendHost::Core::DoUpdateEnabledTypes, core_.get(),
-                 enabled_types));
-}
+                 configured_types));
 
-bool SyncBackendHost::IsDownloadingNigoriForTest() const {
-  return initialization_state_ == DOWNLOADING_NIGORI;
+  if (!ready_task.is_null())
+    ready_task.Run(failed_configuration_types);
 }
 
 SyncBackendHost::DoInitializeOptions::DoInitializeOptions(
     MessageLoop* sync_loop,
     SyncBackendRegistrar* registrar,
     const ModelSafeRoutingInfo& routing_info,
     const std::vector<ModelSafeWorker*>& workers,
     ExtensionsActivityMonitor* extensions_activity_monitor,
     const WeakHandle<JsEventHandler>& event_handler,
     const GURL& service_url,
@@ skipping 36 matching lines @@
       sync_loop_(NULL),
       registrar_(NULL) {
   DCHECK(backend.get());
 }
 
 SyncBackendHost::Core::~Core() {
   DCHECK(!sync_manager_.get());
   DCHECK(!sync_loop_);
 }
 
-SyncBackendHost::PendingConfigureDataTypesState::
-PendingConfigureDataTypesState()
-    : reason(sync_api::CONFIGURE_REASON_UNKNOWN),
-      retry_in_progress(false) {}
-
-SyncBackendHost::PendingConfigureDataTypesState::
-~PendingConfigureDataTypesState() {}
-
 void SyncBackendHost::Core::OnSyncCycleCompleted(
     const SyncSessionSnapshot& snapshot) {
   if (!sync_loop_)
     return;
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   host_.Call(
       FROM_HERE,
       &SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop,
       snapshot);
 }
@@ skipping 231 matching lines @@
     const ModelSafeRoutingInfo& routing_info) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   sync_manager_->StartSyncingNormally(routing_info);
 }
 
 void SyncBackendHost::Core::DoRequestClearServerData() {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   sync_manager_->RequestClearServerData();
 }
 
-void SyncBackendHost::Core::DoRequestCleanupDisabledTypes(
-    const browser_sync::ModelSafeRoutingInfo& routing_info) {
-  DCHECK_EQ(MessageLoop::current(), sync_loop_);
-  sync_manager_->RequestCleanupDisabledTypes(routing_info);
-}
-
 void SyncBackendHost::Core::DoSetEncryptionPassphrase(
     const std::string& passphrase,
     bool is_explicit) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   sync_manager_->SetEncryptionPassphrase(passphrase, is_explicit);
 }
 
 void SyncBackendHost::Core::DoSetDecryptionPassphrase(
     const std::string& passphrase) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
@@ skipping 31 matching lines @@
   registrar_ = NULL;
 
   if (sync_disabled)
     DeleteSyncDataFolder();
 
   sync_loop_ = NULL;
 
   host_.Reset();
 }
 
-void SyncBackendHost::Core::DoRequestConfig(
-    const browser_sync::ModelSafeRoutingInfo& routing_info,
+void SyncBackendHost::Core::DoConfigureSyncer(
+    sync_api::ConfigureReason reason,
     syncable::ModelTypeSet types_to_config,
-    sync_api::ConfigureReason reason) {
+    const browser_sync::ModelSafeRoutingInfo routing_info,
+    const base::Callback<void(syncable::ModelTypeSet)>& ready_task,
+    const base::Closure& retry_callback) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
-  sync_manager_->RequestConfig(routing_info, types_to_config, reason);
+  sync_manager_->ConfigureSyncer(
+      reason,
+      types_to_config,
+      routing_info,
+      base::Bind(&SyncBackendHost::Core::DoFinishConfigureDataTypes,
+                 this,
+                 types_to_config,
+                 ready_task),
+      base::Bind(&SyncBackendHost::Core::DoRetryConfiguration,
+                 this,
+                 retry_callback));
 }
 
-void SyncBackendHost::Core::DoStartConfiguration(
-    const base::Closure& callback) {
+void SyncBackendHost::Core::DoFinishConfigureDataTypes(
+    syncable::ModelTypeSet types_to_config,
+    const base::Callback<void(syncable::ModelTypeSet)>& ready_task) {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
-  sync_manager_->StartConfigurationMode(callback);
+  syncable::ModelTypeSet configured_types =
+      sync_manager_->InitialSyncEndedTypes();
+  configured_types.RetainAll(types_to_config);
+  host_.Call(FROM_HERE,
+             &SyncBackendHost::FinishConfigureDataTypesOnFrontendLoop,
+             types_to_config,
+             configured_types,
+             ready_task);
+}
+
+void SyncBackendHost::Core::DoRetryConfiguration(
+    const base::Closure& retry_callback) {
+  DCHECK_EQ(MessageLoop::current(), sync_loop_);
+  host_.Call(FROM_HERE,
+             &SyncBackendHost::RetryConfigurationOnFrontendLoop,
+             retry_callback);
 }
 
 void SyncBackendHost::Core::DeleteSyncDataFolder() {
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   if (file_util::DirectoryExists(sync_data_folder_path_)) {
     if (!file_util::Delete(sync_data_folder_path_, true))
       SLOG(DFATAL) << "Could not delete the Sync Data folder.";
   }
 }
 
-void SyncBackendHost::Core::FinishConfigureDataTypes() {
-  DCHECK_EQ(MessageLoop::current(), sync_loop_);
-  host_.Call(
-      FROM_HERE,
-      &SyncBackendHost::FinishConfigureDataTypesOnFrontendLoop);
-}
-
 void SyncBackendHost::Core::StartSavingChanges() {
   // We may already be shut down.
   if (!sync_loop_)
     return;
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   DCHECK(!save_changes_timer_.get());
   save_changes_timer_.reset(new base::RepeatingTimer<Core>());
   save_changes_timer_->Start(FROM_HERE,
       base::TimeDelta::FromSeconds(kSaveChangesIntervalSeconds),
       this, &Core::SaveChanges);
@@ skipping 30 matching lines @@
   if (initialization_state_ == CREATING_SYNC_MANAGER)
     initialization_state_ = NOT_INITIALIZED;
 
   DCHECK_EQ(MessageLoop::current(), frontend_loop_);
   if (!success) {
     initialization_state_ = NOT_INITIALIZED;
     frontend_->OnBackendInitialized(WeakHandle<JsBackend>(), false);
     return;
   }
 
-  // If setup has completed, start off in DOWNLOADING_NIGORI so that
-  // we start off by refreshing nigori.
-  CHECK(sync_prefs_.get());
-  if (sync_prefs_->HasSyncSetupCompleted() &&
-      initialization_state_ < DOWNLOADING_NIGORI) {
-    initialization_state_ = DOWNLOADING_NIGORI;
-  }
-
   // Run initialization state machine.
   switch (initialization_state_) {
     case NOT_INITIALIZED:
       initialization_state_ = DOWNLOADING_NIGORI;
       ConfigureDataTypes(
           sync_api::CONFIGURE_REASON_NEW_CLIENT,
           syncable::ModelTypeSet(),
           syncable::ModelTypeSet(),
           WITH_NIGORI,
           // Calls back into this function.
@@ skipping 20 matching lines @@
       // experimental types to enable. This should be done before we inform
       // the frontend to ensure they're visible in the customize screen.
       AddExperimentalTypes();
       frontend_->OnBackendInitialized(js_backend, true);
       break;
     default:
       NOTREACHED();
   }
 }
 
+void SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop(
+    const SyncSessionSnapshot& snapshot) {
+  if (!frontend_)
+    return;
+  DCHECK_EQ(MessageLoop::current(), frontend_loop_);
+
+  last_snapshot_ = snapshot;
+
+  SDVLOG(1) << "Got snapshot " << snapshot.ToString();
+
+  const syncable::ModelTypeSet to_migrate =
+      snapshot.syncer_status().types_needing_local_migration;
+  if (!to_migrate.Empty())
+    frontend_->OnMigrationNeededForTypes(to_migrate);
+
+  // Process any changes to the datatypes we're syncing.
+  // TODO(sync): add support for removing types.
+  if (initialized())
+    AddExperimentalTypes();
+
+  if (initialized())
+    frontend_->OnSyncCycleCompleted();
+}
+
+void SyncBackendHost::RetryConfigurationOnFrontendLoop(
+    const base::Closure& retry_callback) {
+  SDVLOG(1) << "Failed to complete configuration, informing of retry.";
+  retry_callback.Run();
+}
+
 void SyncBackendHost::PersistEncryptionBootstrapToken(
     const std::string& token) {
   CHECK(sync_prefs_.get());
   sync_prefs_->SetEncryptionBootstrapToken(token);
 }
 
 void SyncBackendHost::HandleActionableErrorEventOnFrontendLoop(
     const browser_sync::SyncProtocolError& sync_error) {
   if (!frontend_)
     return;
@@ skipping 120 matching lines @@
       FROM_HERE,
       base::Bind(&SyncBackendHost::Core::DoRefreshNigori,
                  core_.get(), sync_thread_done_callback));
 }
 
 #undef SDVLOG
 
 #undef SLOG
 
 }  // namespace browser_sync