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

components/browser_sync/profile_sync_components_factory_impl.cc

Index: components/browser_sync/profile_sync_components_factory_impl.cc
diff --git a/components/browser_sync/profile_sync_components_factory_impl.cc b/components/browser_sync/profile_sync_components_factory_impl.cc
index 19a0187b149c420e7d1d44fc7d32ba46e5b47b7b..5a55d2c1771d5390d58137c86eb6d851883b1e3c 100644
--- a/components/browser_sync/profile_sync_components_factory_impl.cc
+++ b/components/browser_sync/profile_sync_components_factory_impl.cc
@@ -313,8 +313,8 @@ ProfileSyncComponentsFactoryImpl::CreateSyncBackendHost(
     invalidation::InvalidationService* invalidator,
     const base::WeakPtr<syncer::SyncPrefs>& sync_prefs,
     const base::FilePath& sync_folder) {
-  return new syncer::SyncBackendHostImpl(name, sync_client_, ui_thread_,
-                                         invalidator, sync_prefs, sync_folder);
+  return new syncer::SyncBackendHostImpl(name, sync_client_, invalidator,
+                                         sync_prefs, sync_folder);
 }
 
 std::unique_ptr<syncer::LocalDeviceInfoProvider>