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

ui/accessibility/platform/atk_util_auralinux.h

Index: ui/accessibility/platform/atk_util_auralinux.h
diff --git a/ui/accessibility/platform/atk_util_auralinux.h b/ui/accessibility/platform/atk_util_auralinux.h
index 349c41a53de07af1061fbb44f598efdb221be2e4..8ecb16685e618c19a8b87ecd38a6db307f30011a 100644
--- a/ui/accessibility/platform/atk_util_auralinux.h
+++ b/ui/accessibility/platform/atk_util_auralinux.h
@@ -8,6 +8,10 @@
 #include "base/memory/singleton.h"
 #include "ui/accessibility/ax_export.h"
 
+namespace base {
+class TaskRunner;
+}
+
 namespace ui {
 
 // This singleton class initializes ATK (accessibility toolkit) and
@@ -21,6 +25,8 @@ class AtkUtilAuraLinux {
   AtkUtilAuraLinux();
   virtual ~AtkUtilAuraLinux();
 
+  void Initialize(scoped_refptr<base::TaskRunner> init_task_runner);
+
  private:
   friend struct DefaultSingletonTraits<AtkUtilAuraLinux>;
 };