Enable native accessible touch support inside of ARC

ash/ash_touch_exploration_manager_chromeos.h

Index: ash/ash_touch_exploration_manager_chromeos.h
diff --git a/ash/ash_touch_exploration_manager_chromeos.h b/ash/ash_touch_exploration_manager_chromeos.h
index 8b2aa00018cf3be2902d51482b7a12e68cab54d3..1c4af26c224dc1234d06961604215f4e50ad3aa3 100644
--- a/ash/ash_touch_exploration_manager_chromeos.h
+++ b/ash/ash_touch_exploration_manager_chromeos.h
@@ -76,6 +76,7 @@ class ASH_EXPORT AshTouchExplorationManager
   std::unique_ptr<ui::TouchAccessibilityEnabler> touch_accessibility_enabler_;
   RootWindowController* root_window_controller_;
   chromeos::CrasAudioHandler* audio_handler_;
+  const bool enable_chromevox_arc_support_;
 
   DISALLOW_COPY_AND_ASSIGN(AshTouchExplorationManager);
 };