Pass a TaskRunner through ViewsDelegate to put AX init on FILE thread

ui/accessibility/platform/atk_util_auralinux.cc

Index: ui/accessibility/platform/atk_util_auralinux.cc
diff --git a/ui/accessibility/platform/atk_util_auralinux.cc b/ui/accessibility/platform/atk_util_auralinux.cc
index 7fcaf219351289fe7eba1f670d7a6743a8b40ddc..5d25c510e3258a7a990185f625cfc181eb1ad462 100644
--- a/ui/accessibility/platform/atk_util_auralinux.cc
+++ b/ui/accessibility/platform/atk_util_auralinux.cc
@@ -140,6 +140,14 @@ AtkUtilAuraLinux* AtkUtilAuraLinux::GetInstance() {
 }
 
 AtkUtilAuraLinux::AtkUtilAuraLinux() {
+}
+
+void AtkUtilAuraLinux::Initialize(
+    scoped_refptr<base::TaskRunner> init_task_runner) {
+  // TODO(k.czech): use |init_task_runner| to post a task to do the
+  // initialization rather than doing it on this thread.
+  // http://crbug.com/468112
+
   // Register our util class.
   g_type_class_unref(g_type_class_ref(ATK_UTIL_AURALINUX_TYPE));