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

components/sync/driver/glue/sync_backend_host_impl_unittest.cc

Index: components/sync/driver/glue/sync_backend_host_impl_unittest.cc
diff --git a/components/sync/driver/glue/sync_backend_host_impl_unittest.cc b/components/sync/driver/glue/sync_backend_host_impl_unittest.cc
index 8305afdaa3da129499af8be47238b02cfd9b2baa..75e77d1331ba88bd763aa5fb829fe93d4090783f 100644
--- a/components/sync/driver/glue/sync_backend_host_impl_unittest.cc
+++ b/components/sync/driver/glue/sync_backend_host_impl_unittest.cc
@@ -213,9 +213,10 @@ class SyncBackendHostTest : public testing::Test {
                        base::Unretained(network_resources_.get()), nullptr,
                        base::Bind(&EmptyNetworkTimeUpdate));
     backend_->Initialize(
-        &mock_frontend_, &sync_thread_, WeakHandle<JsEventHandler>(),
-        GURL(std::string()), std::string(), credentials_, true, false,
-        base::FilePath(), std::move(fake_manager_factory_),
+        &mock_frontend_, sync_thread_.task_runner(),
+        WeakHandle<JsEventHandler>(), GURL(std::string()), std::string(),
+        credentials_, true, false, base::FilePath(),
+        std::move(fake_manager_factory_),
         MakeWeakHandle(test_unrecoverable_error_handler_.GetWeakPtr()),
         base::Closure(), http_post_provider_factory_getter,
         std::move(saved_nigori_state_));