[Sync] Pass a TaskRunner into SBHI/SBHC, not a thread or message loop.

components/sync/driver/glue/sync_backend_host_impl.cc

Index: components/sync/driver/glue/sync_backend_host_impl.cc
diff --git a/components/sync/driver/glue/sync_backend_host_impl.cc b/components/sync/driver/glue/sync_backend_host_impl.cc
index d8b2d4b332b6d4dd34218430e1d93418c10890d4..119fcb13cd392799dfd95e718e98eaeb61bbc8d7 100644
--- a/components/sync/driver/glue/sync_backend_host_impl.cc
+++ b/components/sync/driver/glue/sync_backend_host_impl.cc
@@ -72,7 +72,7 @@ SyncBackendHostImpl::~SyncBackendHostImpl() {
 
 void SyncBackendHostImpl::Initialize(
     SyncFrontend* frontend,
-    base::Thread* sync_thread,
+    scoped_refptr<base::SingleThreadTaskRunner> sync_task_runner,
     const WeakHandle<JsEventHandler>& event_handler,
     const GURL& sync_service_url,
     const std::string& sync_user_agent,
@@ -85,8 +85,8 @@ void SyncBackendHostImpl::Initialize(
     const base::Closure& report_unrecoverable_error_function,
     const HttpPostProviderFactoryGetter& http_post_provider_factory_getter,
     std::unique_ptr<SyncEncryptionHandler::NigoriState> saved_nigori_state) {
-  CHECK(sync_thread);
-  sync_thread_ = sync_thread;
+  CHECK(sync_task_runner);
+  sync_task_runner_ = sync_task_runner;
 
   registrar_ = base::MakeUnique<SyncBackendRegistrar>(
       name_, base::Bind(&SyncClient::CreateModelWorkerForGroup,
@@ -120,7 +120,7 @@ void SyncBackendHostImpl::Initialize(
   sync_prefs_->GetInvalidationVersions(&invalidation_versions);
 
   std::unique_ptr<DoInitializeOptions> init_opts(new DoInitializeOptions(
-      sync_thread_->message_loop(), registrar_.get(), workers,
+      sync_task_runner_, registrar_.get(), workers,
       sync_client_->GetExtensionsActivity(), event_handler, sync_service_url,
       sync_user_agent, http_post_provider_factory_getter.Run(
                            core_->GetRequestContextCancelationSignal()),
@@ -138,15 +138,14 @@ void SyncBackendHostImpl::Initialize(
 
 void SyncBackendHostImpl::TriggerRefresh(const ModelTypeSet& types) {
   DCHECK(ui_thread_->BelongsToCurrentThread());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoRefreshTypes, core_, types));
 }
 
 void SyncBackendHostImpl::UpdateCredentials(
     const SyncCredentials& credentials) {
-  DCHECK(sync_thread_->IsRunning());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoUpdateCredentials, core_,
                             credentials));
 }
@@ -157,14 +156,13 @@ void SyncBackendHostImpl::StartSyncingWithServer() {
   ModelSafeRoutingInfo routing_info;
   registrar_->GetModelSafeRoutingInfo(&routing_info);
 
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoStartSyncing, core_,
                             routing_info, sync_prefs_->GetLastPollTime()));
 }
 
 void SyncBackendHostImpl::SetEncryptionPassphrase(const std::string& passphrase,
                                                   bool is_explicit) {
-  DCHECK(sync_thread_->IsRunning());
   if (!IsNigoriEnabled()) {
     NOTREACHED() << "SetEncryptionPassphrase must never be called when nigori"
                     " is disabled.";
@@ -183,7 +181,7 @@ void SyncBackendHostImpl::SetEncryptionPassphrase(const std::string& passphrase,
          cached_passphrase_type_ == PassphraseType::IMPLICIT_PASSPHRASE);
 
   // Post an encryption task on the syncer thread.
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoSetEncryptionPassphrase,
                             core_, passphrase, is_explicit));
 }
@@ -212,7 +210,7 @@ bool SyncBackendHostImpl::SetDecryptionPassphrase(
     return false;
 
   // Post a decryption task on the syncer thread.
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoSetDecryptionPassphrase,
                             core_, passphrase));
 
@@ -235,8 +233,6 @@ void SyncBackendHostImpl::StopSyncingForShutdown() {
   // Immediately stop sending messages to the frontend.
   frontend_ = nullptr;
 
-  DCHECK(sync_thread_->IsRunning());
-
   registrar_->RequestWorkerStopOnUIThread();
 
   core_->ShutdownOnUIThread();
@@ -246,7 +242,6 @@ void SyncBackendHostImpl::Shutdown(ShutdownReason reason) {
   // StopSyncingForShutdown() (which nulls out |frontend_|) should be
   // called first.
   DCHECK(!frontend_);
-  DCHECK(sync_thread_->IsRunning());
 
   if (invalidation_handler_registered_) {
     if (reason == DISABLE_SYNC) {
@@ -262,12 +257,12 @@ void SyncBackendHostImpl::Shutdown(ShutdownReason reason) {
   // Shut down and destroy SyncManager. SyncManager holds a pointer to
   // |registrar_| so its destruction must be sequenced before the destruction of
   // |registrar_|.
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoShutdown, core_, reason));
   core_ = nullptr;
 
   // Destroy |registrar_|.
-  sync_thread_->task_runner()->DeleteSoon(FROM_HERE, registrar_.release());
+  sync_task_runner_->DeleteSoon(FROM_HERE, registrar_.release());
 }
 
 void SyncBackendHostImpl::UnregisterInvalidationIds() {
@@ -391,7 +386,7 @@ ModelTypeSet SyncBackendHostImpl::ConfigureDataTypes(
 }
 
 void SyncBackendHostImpl::EnableEncryptEverything() {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoEnableEncryptEverything, core_));
 }
@@ -468,12 +463,12 @@ void SyncBackendHostImpl::GetModelSafeRoutingInfo(
 
 void SyncBackendHostImpl::FlushDirectory() const {
   DCHECK(initialized());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::SaveChanges, core_));
 }
 
 void SyncBackendHostImpl::RequestBufferedProtocolEventsAndEnableForwarding() {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(
           &SyncBackendHostCore::SendBufferedProtocolEventsAndEnableForwarding,
@@ -481,14 +476,14 @@ void SyncBackendHostImpl::RequestBufferedProtocolEventsAndEnableForwarding() {
 }
 
 void SyncBackendHostImpl::DisableProtocolEventForwarding() {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DisableProtocolEventForwarding, core_));
 }
 
 void SyncBackendHostImpl::EnableDirectoryTypeDebugInfoForwarding() {
   DCHECK(initialized());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::EnableDirectoryTypeDebugInfoForwarding,
                  core_));
@@ -496,7 +491,7 @@ void SyncBackendHostImpl::EnableDirectoryTypeDebugInfoForwarding() {
 
 void SyncBackendHostImpl::DisableDirectoryTypeDebugInfoForwarding() {
   DCHECK(initialized());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DisableDirectoryTypeDebugInfoForwarding,
                  core_));
@@ -504,7 +499,7 @@ void SyncBackendHostImpl::DisableDirectoryTypeDebugInfoForwarding() {
 
 void SyncBackendHostImpl::InitCore(
     std::unique_ptr<DoInitializeOptions> options) {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoInitialize, core_,
                             base::Passed(&options)));
 }
@@ -524,7 +519,7 @@ void SyncBackendHostImpl::RequestConfigureSyncer(
   config_types.to_purge = to_purge;
   config_types.to_journal = to_journal;
   config_types.to_unapply = to_unapply;
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoConfigureSyncer, core_, reason,
                  config_types, routing_info, ready_task, retry_callback));
@@ -650,14 +645,14 @@ void SyncBackendHostImpl::HandleMigrationRequestedOnFrontendLoop(
 }
 
 void SyncBackendHostImpl::OnInvalidatorStateChange(InvalidatorState state) {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoOnInvalidatorStateChange,
                             core_, state));
 }
 
 void SyncBackendHostImpl::OnIncomingInvalidation(
     const ObjectIdInvalidationMap& invalidation_map) {
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoOnIncomingInvalidation,
                             core_, invalidation_map));
 }
@@ -786,7 +781,7 @@ void SyncBackendHostImpl::UpdateInvalidationVersions(
 void SyncBackendHostImpl::RefreshTypesForTest(ModelTypeSet types) {
   DCHECK(ui_thread_->BelongsToCurrentThread());
 
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoRefreshTypes, core_, types));
 }
@@ -794,7 +789,7 @@ void SyncBackendHostImpl::RefreshTypesForTest(ModelTypeSet types) {
 void SyncBackendHostImpl::ClearServerData(
     const SyncManager::ClearServerDataCallback& callback) {
   DCHECK(ui_thread_->BelongsToCurrentThread());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoClearServerData, core_, callback));
 }
@@ -802,7 +797,7 @@ void SyncBackendHostImpl::ClearServerData(
 void SyncBackendHostImpl::OnCookieJarChanged(bool account_mismatch,
                                              bool empty_jar) {
   DCHECK(ui_thread_->BelongsToCurrentThread());
-  sync_thread_->task_runner()->PostTask(
+  sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoOnCookieJarChanged, core_,
                             account_mismatch, empty_jar));
 }