Refactor SyncBackendHost

chrome/browser/sync/glue/sync_backend_host_impl.cc

Index: chrome/browser/sync/glue/sync_backend_host_impl.cc
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl.cc b/chrome/browser/sync/glue/sync_backend_host_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f9e7ff4905d7c95ca1fe2c3644753022853f570a
--- /dev/null
+++ b/chrome/browser/sync/glue/sync_backend_host_impl.cc
@@ -0,0 +1,763 @@
+// Copyright 2013 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 "chrome/browser/sync/glue/sync_backend_host_impl.h"
+
+#include "base/command_line.h"
+#include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/invalidation/invalidation_service.h"
+#include "chrome/browser/invalidation/invalidation_service_factory.h"
+#include "chrome/browser/network_time/network_time_tracker.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sync/glue/sync_backend_host_core.h"
+#include "chrome/browser/sync/glue/sync_backend_registrar.h"
+#include "chrome/browser/sync/glue/sync_frontend.h"
+#include "chrome/browser/sync/sync_prefs.h"
+#include "chrome/common/chrome_switches.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_source.h"
+#include "sync/internal_api/public/base_transaction.h"
+#include "sync/internal_api/public/http_bridge.h"
+#include "sync/internal_api/public/internal_components_factory.h"
+#include "sync/internal_api/public/internal_components_factory_impl.h"
+#include "sync/internal_api/public/sync_manager.h"
+#include "sync/internal_api/public/sync_manager_factory.h"
+#include "sync/internal_api/public/util/experiments.h"
+#include "sync/internal_api/public/util/sync_string_conversions.h"
+
+// Helper macros to log with the syncer thread name; useful when there
+// are multiple syncers involved.
+
+#define SLOG(severity) LOG(severity) << name_ << ": "
+
+#define SDVLOG(verbose_level) DVLOG(verbose_level) << name_ << ": "
+
+using syncer::InternalComponentsFactory;
+
+static const base::FilePath::CharType kSyncDataFolderName[] =
+    FILE_PATH_LITERAL("Sync Data");
+
+namespace browser_sync {
+
+SyncBackendHostImpl::SyncBackendHostImpl(
+    const std::string& name,
+    Profile* profile,
+    const base::WeakPtr<SyncPrefs>& sync_prefs)
+    : frontend_loop_(base::MessageLoop::current()),
+      profile_(profile),
+      name_(name),
+      initialized_(false),
+      sync_prefs_(sync_prefs),
+      frontend_(NULL),
+      cached_passphrase_type_(syncer::IMPLICIT_PASSPHRASE),
+      invalidator_(
+          invalidation::InvalidationServiceFactory::GetForProfile(profile)),
+      invalidation_handler_registered_(false),
+      weak_ptr_factory_(this) {
+  core_ = new SyncBackendHostCore(
+      name_,
+      profile_->GetPath().Append(kSyncDataFolderName),
+      sync_prefs_->HasSyncSetupCompleted(),
+      weak_ptr_factory_.GetWeakPtr());
+}
+
+SyncBackendHostImpl::~SyncBackendHostImpl() {
+  DCHECK(!core_.get() && !frontend_) << "Must call Shutdown before destructor.";
+  DCHECK(!registrar_.get());
+}
+
+void SyncBackendHostImpl::Initialize(
+    SyncFrontend* frontend,
+    scoped_ptr<base::Thread> sync_thread,
+    const syncer::WeakHandle<syncer::JsEventHandler>& event_handler,
+    const GURL& sync_service_url,
+    const syncer::SyncCredentials& credentials,
+    bool delete_sync_data_folder,
+    scoped_ptr<syncer::SyncManagerFactory> sync_manager_factory,
+    scoped_ptr<syncer::UnrecoverableErrorHandler> unrecoverable_error_handler,
+    syncer::ReportUnrecoverableErrorFunction
+        report_unrecoverable_error_function) {
+  registrar_.reset(new browser_sync::SyncBackendRegistrar(name_,
+                                            profile_,
+                                            sync_thread.Pass()));
+  CHECK(registrar_->sync_thread());
+
+  frontend_ = frontend;
+  DCHECK(frontend);
+
+  syncer::ModelSafeRoutingInfo routing_info;
+  std::vector<syncer::ModelSafeWorker*> workers;
+  registrar_->GetModelSafeRoutingInfo(&routing_info);
+  registrar_->GetWorkers(&workers);
+
+  InternalComponentsFactory::Switches factory_switches = {
+    InternalComponentsFactory::ENCRYPTION_KEYSTORE,
+    InternalComponentsFactory::BACKOFF_NORMAL
+  };
+
+  CommandLine* cl = CommandLine::ForCurrentProcess();
+  if (cl->HasSwitch(switches::kSyncShortInitialRetryOverride)) {
+    factory_switches.backoff_override =
+        InternalComponentsFactory::BACKOFF_SHORT_INITIAL_RETRY_OVERRIDE;
+  }
+  if (cl->HasSwitch(switches::kSyncEnableGetUpdateAvoidance)) {
+    factory_switches.pre_commit_updates_policy =
+        InternalComponentsFactory::FORCE_ENABLE_PRE_COMMIT_UPDATE_AVOIDANCE;
+  }
+
+  scoped_ptr<DoInitializeOptions> init_opts(new DoInitializeOptions(
+      registrar_->sync_thread()->message_loop(),
+      registrar_.get(),
+      routing_info,
+      workers,
+      extensions_activity_monitor_.GetExtensionsActivity(),
+      event_handler,
+      sync_service_url,
+      scoped_ptr<syncer::HttpPostProviderFactory>(
+          new syncer::HttpBridgeFactory(
+              make_scoped_refptr(profile_->GetRequestContext()),
+              NetworkTimeTracker::BuildNotifierUpdateCallback(),
+              core_->GetRequestContextCancelationSignal())),
+      credentials,
+      invalidator_->GetInvalidatorClientId(),
+      sync_manager_factory.Pass(),
+      delete_sync_data_folder,
+      sync_prefs_->GetEncryptionBootstrapToken(),
+      sync_prefs_->GetKeystoreEncryptionBootstrapToken(),
+      scoped_ptr<InternalComponentsFactory>(
+          new syncer::InternalComponentsFactoryImpl(factory_switches)).Pass(),
+      unrecoverable_error_handler.Pass(),
+      report_unrecoverable_error_function));
+  InitCore(init_opts.Pass());
+}
+
+void SyncBackendHostImpl::UpdateCredentials(
+    const syncer::SyncCredentials& credentials) {
+  DCHECK(registrar_->sync_thread()->IsRunning());
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoUpdateCredentials,
+                 core_.get(),
+                 credentials));
+}
+
+void SyncBackendHostImpl::StartSyncingWithServer() {
+  SDVLOG(1) << "SyncBackendHostImpl::StartSyncingWithServer called.";
+
+  syncer::ModelSafeRoutingInfo routing_info;
+  registrar_->GetModelSafeRoutingInfo(&routing_info);
+
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoStartSyncing,
+                 core_.get(), routing_info));
+}
+
+void SyncBackendHostImpl::SetEncryptionPassphrase(const std::string& passphrase,
+                                              bool is_explicit) {
+  DCHECK(registrar_->sync_thread()->IsRunning());
+  if (!IsNigoriEnabled()) {
+    NOTREACHED() << "SetEncryptionPassphrase must never be called when nigori"
+                    " is disabled.";
+    return;
+  }
+
+  // We should never be called with an empty passphrase.
+  DCHECK(!passphrase.empty());
+
+  // This should only be called by the frontend.
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  // SetEncryptionPassphrase should never be called if we are currently
+  // encrypted with an explicit passphrase.
+  DCHECK(cached_passphrase_type_ == syncer::KEYSTORE_PASSPHRASE ||
+         cached_passphrase_type_ == syncer::IMPLICIT_PASSPHRASE);
+
+  // Post an encryption task on the syncer thread.
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoSetEncryptionPassphrase,
+                 core_.get(),
+                 passphrase, is_explicit));
+}
+
+bool SyncBackendHostImpl::SetDecryptionPassphrase(
+    const std::string& passphrase) {
+  if (!IsNigoriEnabled()) {
+    NOTREACHED() << "SetDecryptionPassphrase must never be called when nigori"
+                    " is disabled.";
+    return false;
+  }
+
+  // We should never be called with an empty passphrase.
+  DCHECK(!passphrase.empty());
+
+  // This should only be called by the frontend.
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  // This should only be called when we have cached pending keys.
+  DCHECK(cached_pending_keys_.has_blob());
+
+  // Check the passphrase that was provided against our local cache of the
+  // cryptographer's pending keys. If this was unsuccessful, the UI layer can
+  // immediately call OnPassphraseRequired without showing the user a spinner.
+  if (!CheckPassphraseAgainstCachedPendingKeys(passphrase))
+    return false;
+
+  // Post a decryption task on the syncer thread.
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoSetDecryptionPassphrase,
+                 core_.get(),
+                 passphrase));
+
+  // Since we were able to decrypt the cached pending keys with the passphrase
+  // provided, we immediately alert the UI layer that the passphrase was
+  // accepted. This will avoid the situation where a user enters a passphrase,
+  // clicks OK, immediately reopens the advanced settings dialog, and gets an
+  // unnecessary prompt for a passphrase.
+  // Note: It is not guaranteed that the passphrase will be accepted by the
+  // syncer thread, since we could receive a new nigori node while the task is
+  // pending. This scenario is a valid race, and SetDecryptionPassphrase can
+  // trigger a new OnPassphraseRequired if it needs to.
+  NotifyPassphraseAccepted();
+  return true;
+}
+
+void SyncBackendHostImpl::StopSyncingForShutdown() {
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  // Immediately stop sending messages to the frontend.
+  frontend_ = NULL;
+
+  // Stop listening for and forwarding locally-triggered sync refresh requests.
+  notification_registrar_.RemoveAll();
+
+  DCHECK(registrar_->sync_thread()->IsRunning());
+
+  registrar_->RequestWorkerStopOnUIThread();
+
+  core_->ShutdownOnUIThread();
+}
+
+scoped_ptr<base::Thread> SyncBackendHostImpl::Shutdown(ShutdownOption option) {
+  // StopSyncingForShutdown() (which nulls out |frontend_|) should be
+  // called first.
+  DCHECK(!frontend_);
+  DCHECK(registrar_->sync_thread()->IsRunning());
+
+  bool sync_disabled = (option == DISABLE_AND_CLAIM_THREAD);
+  bool sync_thread_claimed =
+      (option == DISABLE_AND_CLAIM_THREAD || option == STOP_AND_CLAIM_THREAD);
+
+  if (invalidation_handler_registered_) {
+    if (sync_disabled) {
+      UnregisterInvalidationIds();
+    }
+    invalidator_->UnregisterInvalidationHandler(this);
+    invalidator_ = NULL;
+  }
+  invalidation_handler_registered_ = false;
+
+  // Shut down and destroy sync manager.
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoShutdown,
+                 core_.get(), sync_disabled));
+  core_ = NULL;
+
+  // Worker cleanup.
+  SyncBackendRegistrar* detached_registrar = registrar_.release();
+  detached_registrar->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(&SyncBackendRegistrar::Shutdown,
+                 base::Unretained(detached_registrar)));
+
+  if (sync_thread_claimed)
+    return detached_registrar->ReleaseSyncThread();
+  else
+    return scoped_ptr<base::Thread>();
+}
+
+void SyncBackendHostImpl::UnregisterInvalidationIds() {
+  if (invalidation_handler_registered_) {
+    invalidator_->UpdateRegisteredInvalidationIds(
+        this,
+        syncer::ObjectIdSet());
+  }
+}
+
+void SyncBackendHostImpl::ConfigureDataTypes(
+    syncer::ConfigureReason reason,
+    const DataTypeConfigStateMap& config_state_map,
+    const base::Callback<void(syncer::ModelTypeSet,
+                              syncer::ModelTypeSet)>& ready_task,
+    const base::Callback<void()>& retry_callback) {
+  // Only one configure is allowed at a time.  This is guaranteed by our
+  // callers.  The SyncBackendHostImpl requests one configure as the backend is
+  // initializing and waits for it to complete.  After initialization, all
+  // configurations will pass through the DataTypeManager, which is careful to
+  // never send a new configure request until the current request succeeds.
+
+  // The SyncBackendRegistrar's routing info will be updated by adding the
+  // types_to_add to the list then removing types_to_remove.  Any types which
+  // are not in either of those sets will remain untouched.
+  //
+  // Types which were not in the list previously are not fully downloaded, so we
+  // must ask the syncer to download them.  Any newly supported datatypes will
+  // not have been in that routing info list, so they will be among the types
+  // downloaded if they are enabled.
+  //
+  // The SyncBackendRegistrar's state was initially derived from the types
+  // detected to have been downloaded in the database.  Afterwards it is
+  // modified only by this function.  We expect it to remain in sync with the
+  // backend because configuration requests are never aborted; they are retried
+  // until they succeed or the backend is shut down.
+
+  syncer::ModelTypeSet previous_types = registrar_->GetLastConfiguredTypes();
+
+  syncer::ModelTypeSet disabled_types =
+      GetDataTypesInState(DISABLED, config_state_map);
+  syncer::ModelTypeSet fatal_types =
+      GetDataTypesInState(FATAL, config_state_map);
+  syncer::ModelTypeSet crypto_types =
+      GetDataTypesInState(CRYPTO, config_state_map);
+  disabled_types.PutAll(fatal_types);
+  disabled_types.PutAll(crypto_types);
+  syncer::ModelTypeSet active_types =
+      GetDataTypesInState(CONFIGURE_ACTIVE, config_state_map);
+  syncer::ModelTypeSet clean_first_types =
+      GetDataTypesInState(CONFIGURE_CLEAN, config_state_map);
+  syncer::ModelTypeSet types_to_download = registrar_->ConfigureDataTypes(
+      syncer::Union(active_types, clean_first_types),
+      disabled_types);
+  types_to_download.PutAll(clean_first_types);
+  types_to_download.RemoveAll(syncer::ProxyTypes());
+  if (!types_to_download.Empty())
+    types_to_download.Put(syncer::NIGORI);
+
+  // TODO(sync): crbug.com/137550.
+  // It's dangerous to configure types that have progress markers.  Types with
+  // progress markers can trigger a MIGRATION_DONE response.  We are not
+  // prepared to handle a migration during a configure, so we must ensure that
+  // all our types_to_download actually contain no data before we sync them.
+  //
+  // One common way to end up in this situation used to be types which
+  // downloaded some or all of their data but have not applied it yet.  We avoid
+  // problems with those types by purging the data of any such partially synced
+  // types soon after we load the directory.
+  //
+  // Another possible scenario is that we have newly supported or newly enabled
+  // data types being downloaded here but the nigori type, which is always
+  // included in any GetUpdates request, requires migration.  The server has
+  // code to detect this scenario based on the configure reason, the fact that
+  // the nigori type is the only requested type which requires migration, and
+  // that the requested types list includes at least one non-nigori type.  It
+  // will not send a MIGRATION_DONE response in that case.  We still need to be
+  // careful to not send progress markers for non-nigori types, though.  If a
+  // non-nigori type in the request requires migration, a MIGRATION_DONE
+  // response will be sent.
+
+  syncer::ModelSafeRoutingInfo routing_info;
+  registrar_->GetModelSafeRoutingInfo(&routing_info);
+
+  syncer::ModelTypeSet current_types = registrar_->GetLastConfiguredTypes();
+  syncer::ModelTypeSet types_to_purge =
+      syncer::Difference(previous_types, current_types);
+  syncer::ModelTypeSet inactive_types =
+      GetDataTypesInState(CONFIGURE_INACTIVE, config_state_map);
+  types_to_purge.RemoveAll(inactive_types);
+
+  // If a type has already been disabled and unapplied or journaled, it will
+  // not be part of the |types_to_purge| set, and therefore does not need
+  // to be acted on again.
+  fatal_types.RetainAll(types_to_purge);
+  syncer::ModelTypeSet unapply_types =
+      syncer::Union(crypto_types, clean_first_types);
+  unapply_types.RetainAll(types_to_purge);
+
+  DCHECK(syncer::Intersection(current_types, fatal_types).Empty());
+  DCHECK(syncer::Intersection(current_types, crypto_types).Empty());
+  DCHECK(current_types.HasAll(types_to_download));
+
+  SDVLOG(1) << "Types "
+            << syncer::ModelTypeSetToString(types_to_download)
+            << " added; calling DoConfigureSyncer";
+  // Divide up the types into their corresponding actions (each is mutually
+  // exclusive):
+  // - Types which have just been added to the routing info (types_to_download):
+  //   are downloaded.
+  // - Types which have encountered a fatal error (fatal_types) are deleted
+  //   from the directory and journaled in the delete journal.
+  // - Types which have encountered a cryptographer error (crypto_types) are
+  //   unapplied (local state is purged but sync state is not).
+  // - All other types not in the routing info (types just disabled) are deleted
+  //   from the directory.
+  // - Everything else (enabled types and already disabled types) is not
+  //   touched.
+  RequestConfigureSyncer(reason,
+                         types_to_download,
+                         types_to_purge,
+                         fatal_types,
+                         unapply_types,
+                         inactive_types,
+                         routing_info,
+                         ready_task,
+                         retry_callback);
+}
+
+void SyncBackendHostImpl::EnableEncryptEverything() {
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+     base::Bind(&SyncBackendHostCore::DoEnableEncryptEverything,
+                core_.get()));
+}
+
+void SyncBackendHostImpl::ActivateDataType(
+    syncer::ModelType type, syncer::ModelSafeGroup group,
+    ChangeProcessor* change_processor) {
+  registrar_->ActivateDataType(type, group, change_processor, GetUserShare());
+}
+
+void SyncBackendHostImpl::DeactivateDataType(syncer::ModelType type) {
+  registrar_->DeactivateDataType(type);
+}
+
+syncer::UserShare* SyncBackendHostImpl::GetUserShare() const {
+  return core_->sync_manager()->GetUserShare();
+}
+
+SyncBackendHostImpl::Status SyncBackendHostImpl::GetDetailedStatus() {
+  DCHECK(initialized());
+  return core_->sync_manager()->GetDetailedStatus();
+}
+
+syncer::sessions::SyncSessionSnapshot
+SyncBackendHostImpl::GetLastSessionSnapshot() const {
+  return last_snapshot_;
+}
+
+bool SyncBackendHostImpl::HasUnsyncedItems() const {
+  DCHECK(initialized());
+  return core_->sync_manager()->HasUnsyncedItems();
+}
+
+bool SyncBackendHostImpl::IsNigoriEnabled() const {
+  return registrar_.get() && registrar_->IsNigoriEnabled();
+}
+
+syncer::PassphraseType SyncBackendHostImpl::GetPassphraseType() const {
+  return cached_passphrase_type_;
+}
+
+base::Time SyncBackendHostImpl::GetExplicitPassphraseTime() const {
+  return cached_explicit_passphrase_time_;
+}
+
+bool SyncBackendHostImpl::IsCryptographerReady(
+    const syncer::BaseTransaction* trans) const {
+  return initialized() && trans->GetCryptographer()->is_ready();
+}
+
+void SyncBackendHostImpl::GetModelSafeRoutingInfo(
+    syncer::ModelSafeRoutingInfo* out) const {
+  if (initialized()) {
+    CHECK(registrar_.get());
+    registrar_->GetModelSafeRoutingInfo(out);
+  } else {
+    NOTREACHED();
+  }
+}
+
+SyncedDeviceTracker* SyncBackendHostImpl::GetSyncedDeviceTracker() const {
+  if (!initialized())
+    return NULL;
+  return core_->synced_device_tracker();
+}
+
+void SyncBackendHostImpl::InitCore(scoped_ptr<DoInitializeOptions> options) {
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoInitialize,
+                 core_.get(), base::Passed(&options)));
+}
+
+void SyncBackendHostImpl::RequestConfigureSyncer(
+    syncer::ConfigureReason reason,
+    syncer::ModelTypeSet to_download,
+    syncer::ModelTypeSet to_purge,
+    syncer::ModelTypeSet to_journal,
+    syncer::ModelTypeSet to_unapply,
+    syncer::ModelTypeSet to_ignore,
+    const syncer::ModelSafeRoutingInfo& routing_info,
+    const base::Callback<void(syncer::ModelTypeSet,
+                              syncer::ModelTypeSet)>& ready_task,
+    const base::Closure& retry_callback) {
+  DoConfigureSyncerTypes config_types;
+  config_types.to_download = to_download;
+  config_types.to_purge = to_purge;
+  config_types.to_journal = to_journal;
+  config_types.to_unapply = to_unapply;
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+       base::Bind(&SyncBackendHostCore::DoConfigureSyncer,
+                  core_.get(),
+                  reason,
+                  config_types,
+                  routing_info,
+                  ready_task,
+                  retry_callback));
+}
+
+void SyncBackendHostImpl::FinishConfigureDataTypesOnFrontendLoop(
+    const syncer::ModelTypeSet enabled_types,
+    const syncer::ModelTypeSet succeeded_configuration_types,
+    const syncer::ModelTypeSet failed_configuration_types,
+    const base::Callback<void(syncer::ModelTypeSet,
+                              syncer::ModelTypeSet)>& ready_task) {
+  if (!frontend_)
+    return;
+
+  invalidator_->UpdateRegisteredInvalidationIds(
+      this,
+      ModelTypeSetToObjectIdSet(enabled_types));
+
+  if (!ready_task.is_null())
+    ready_task.Run(succeeded_configuration_types, failed_configuration_types);
+}
+
+void SyncBackendHostImpl::Observe(
+    int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  DCHECK_EQ(type, chrome::NOTIFICATION_SYNC_REFRESH_LOCAL);
+
+  content::Details<const syncer::ModelTypeSet> state_details(details);
+  const syncer::ModelTypeSet& types = *(state_details.ptr());
+  registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoRefreshTypes, core_.get(), types));
+}
+
+void SyncBackendHostImpl::AddExperimentalTypes() {
+  CHECK(initialized());
+  syncer::Experiments experiments;
+  if (core_->sync_manager()->ReceivedExperiment(&experiments))
+    frontend_->OnExperimentsChanged(experiments);
+}
+
+void SyncBackendHostImpl::HandleControlTypesDownloadRetry() {
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  if (!frontend_)
+    return;
+
+  frontend_->OnSyncConfigureRetry();
+}
+
+void SyncBackendHostImpl::HandleInitializationSuccessOnFrontendLoop(
+    const syncer::WeakHandle<syncer::JsBackend> js_backend,
+    const syncer::WeakHandle<syncer::DataTypeDebugInfoListener>
+        debug_info_listener) {
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  if (!frontend_)
+    return;
+
+  initialized_ = true;
+
+  invalidator_->RegisterInvalidationHandler(this);
+  invalidation_handler_registered_ = true;
+
+  // Fake a state change to initialize the SyncManager's cached invalidator
+  // state.
+  OnInvalidatorStateChange(invalidator_->GetInvalidatorState());
+
+  // Start forwarding refresh requests to the SyncManager
+  notification_registrar_.Add(this, chrome::NOTIFICATION_SYNC_REFRESH_LOCAL,
+                              content::Source<Profile>(profile_));
+
+  // Now that we've downloaded the control types, we can see if there are any
+  // 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,
+                                  debug_info_listener,
+                                  true);
+}
+
+void SyncBackendHostImpl::HandleInitializationFailureOnFrontendLoop() {
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  if (!frontend_)
+    return;
+
+  frontend_->OnBackendInitialized(
+      syncer::WeakHandle<syncer::JsBackend>(),
+      syncer::WeakHandle<syncer::DataTypeDebugInfoListener>(),
+      false);
+}
+
+void SyncBackendHostImpl::HandleSyncCycleCompletedOnFrontendLoop(
+    const syncer::sessions::SyncSessionSnapshot& snapshot) {
+  if (!frontend_)
+    return;
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  last_snapshot_ = snapshot;
+
+  SDVLOG(1) << "Got snapshot " << snapshot.ToString();
+
+  const syncer::ModelTypeSet to_migrate =
+      snapshot.model_neutral_state().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 SyncBackendHostImpl::RetryConfigurationOnFrontendLoop(
+    const base::Closure& retry_callback) {
+  SDVLOG(1) << "Failed to complete configuration, informing of retry.";
+  retry_callback.Run();
+}
+
+void SyncBackendHostImpl::PersistEncryptionBootstrapToken(
+    const std::string& token,
+    syncer::BootstrapTokenType token_type) {
+  CHECK(sync_prefs_.get());
+  DCHECK(!token.empty());
+  if (token_type == syncer::PASSPHRASE_BOOTSTRAP_TOKEN)
+    sync_prefs_->SetEncryptionBootstrapToken(token);
+  else
+    sync_prefs_->SetKeystoreEncryptionBootstrapToken(token);
+}
+
+void SyncBackendHostImpl::HandleActionableErrorEventOnFrontendLoop(
+    const syncer::SyncProtocolError& sync_error) {
+  if (!frontend_)
+    return;
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  frontend_->OnActionableError(sync_error);
+}
+
+void SyncBackendHostImpl::OnInvalidatorStateChange(
+    syncer::InvalidatorState state) {
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoOnInvalidatorStateChange,
+                 core_.get(),
+                 state));
+}
+
+void SyncBackendHostImpl::OnIncomingInvalidation(
+    const syncer::ObjectIdInvalidationMap& invalidation_map) {
+  // TODO(rlarocque): Acknowledge these invalidations only after the syncer has
+  // acted on them and saved the results to disk.
+  syncer::ObjectIdSet ids = invalidation_map.GetObjectIds();
+  for (syncer::ObjectIdSet::const_iterator it = ids.begin();
+       it != ids.end(); ++it) {
+    const syncer::AckHandle& handle =
+        invalidation_map.ForObject(*it).back().ack_handle();
+    invalidator_->AcknowledgeInvalidation(*it, handle);
+  }
+
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(&SyncBackendHostCore::DoOnIncomingInvalidation,
+                 core_.get(),
+                 invalidation_map));
+}
+
+bool SyncBackendHostImpl::CheckPassphraseAgainstCachedPendingKeys(
+    const std::string& passphrase) const {
+  DCHECK(cached_pending_keys_.has_blob());
+  DCHECK(!passphrase.empty());
+  syncer::Nigori nigori;
+  nigori.InitByDerivation("localhost", "dummy", passphrase);
+  std::string plaintext;
+  bool result = nigori.Decrypt(cached_pending_keys_.blob(), &plaintext);
+  DVLOG_IF(1, result) << "Passphrase failed to decrypt pending keys.";
+  return result;
+}
+
+void SyncBackendHostImpl::NotifyPassphraseRequired(
+    syncer::PassphraseRequiredReason reason,
+    sync_pb::EncryptedData pending_keys) {
+  if (!frontend_)
+    return;
+
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  // Update our cache of the cryptographer's pending keys.
+  cached_pending_keys_ = pending_keys;
+
+  frontend_->OnPassphraseRequired(reason, pending_keys);
+}
+
+void SyncBackendHostImpl::NotifyPassphraseAccepted() {
+  if (!frontend_)
+    return;
+
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  // Clear our cache of the cryptographer's pending keys.
+  cached_pending_keys_.clear_blob();
+  frontend_->OnPassphraseAccepted();
+}
+
+void SyncBackendHostImpl::NotifyEncryptedTypesChanged(
+    syncer::ModelTypeSet encrypted_types,
+    bool encrypt_everything) {
+  if (!frontend_)
+    return;
+
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  frontend_->OnEncryptedTypesChanged(
+      encrypted_types, encrypt_everything);
+}
+
+void SyncBackendHostImpl::NotifyEncryptionComplete() {
+  if (!frontend_)
+    return;
+
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  frontend_->OnEncryptionComplete();
+}
+
+void SyncBackendHostImpl::HandlePassphraseTypeChangedOnFrontendLoop(
+    syncer::PassphraseType type,
+    base::Time explicit_passphrase_time) {
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  DVLOG(1) << "Passphrase type changed to "
+           << syncer::PassphraseTypeToString(type);
+  cached_passphrase_type_ = type;
+  cached_explicit_passphrase_time_ = explicit_passphrase_time;
+}
+
+void SyncBackendHostImpl::HandleStopSyncingPermanentlyOnFrontendLoop() {
+  if (!frontend_)
+    return;
+  frontend_->OnStopSyncingPermanently();
+}
+
+void SyncBackendHostImpl::HandleConnectionStatusChangeOnFrontendLoop(
+    syncer::ConnectionStatus status) {
+  if (!frontend_)
+    return;
+
+  DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+
+  DVLOG(1) << "Connection status changed: "
+           << syncer::ConnectionStatusToString(status);
+  frontend_->OnConnectionStatusChange(status);
+}
+
+base::MessageLoop* SyncBackendHostImpl::GetSyncLoopForTesting() {
+  return registrar_->sync_thread()->message_loop();
+}
+
+}  // namespace browser_sync
+
+#undef SDVLOG
+
+#undef SLOG
+