Wire up an api to darken screen for accessibility

chrome/browser/ui/aura/accessibility/automation_manager_aura.cc

Index: chrome/browser/ui/aura/accessibility/automation_manager_aura.cc
diff --git a/chrome/browser/ui/aura/accessibility/automation_manager_aura.cc b/chrome/browser/ui/aura/accessibility/automation_manager_aura.cc
index 11f50f0fc4980439abd235909769fa85d0c78be3..a047d1d90c158bbb1090a9556d51f3b218228cd9 100644
--- a/chrome/browser/ui/aura/accessibility/automation_manager_aura.cc
+++ b/chrome/browser/ui/aura/accessibility/automation_manager_aura.cc
@@ -26,6 +26,8 @@
 
 #if defined(OS_CHROMEOS)
 #include "ash/wm/window_util.h"  // nogncheck
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/power_manager_client.h"
 #endif
 
 using content::BrowserContext;
@@ -106,6 +108,14 @@ void AutomationManagerAura::PerformAction(
     case ui::AX_ACTION_SHOW_CONTEXT_MENU:
       current_tree_->ShowContextMenu(data.target_node_id);
       break;
+#if defined(OS_CHROMEOS)
+    case ui::AX_ACTION_TOGGLE_DARKEN_SCREEN:
+      chromeos::DBusThreadManager::Get()
+          ->GetPowerManagerClient()
+          ->SetBacklightsForcedOff(
+              data.GetBoolAttribute(ui::AX_ACTION_ATTR_DARKEN_SCREEN));
+      break;
+#endif
     case ui::AX_ACTION_SET_ACCESSIBILITY_FOCUS:
       // Sent by ChromeVox but doesn't need to be handled by aura.
       break;