Wire up an api to darken screen for accessibility

chrome/browser/accessibility/accessibility_extension_api.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_EXTENSION_API_H_
 #define CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_EXTENSION_API_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 23 matching lines @@
 
 // API function that sets keyboard capture mode.
 class AccessibilityPrivateSetKeyboardListenerFunction
     : public UIThreadExtensionFunction {
   ~AccessibilityPrivateSetKeyboardListenerFunction() override {}
   ResponseAction Run() override;
   DECLARE_EXTENSION_FUNCTION("accessibilityPrivate.setKeyboardListener",
                              ACCESSIBILITY_PRIVATE_SETKEYBOARDLISTENER)
 };
 
+// API function that darkens or undarkens the screen.
+class AccessibilityPrivateDarkenScreenFunction
+    : public UIThreadExtensionFunction {
+  ~AccessibilityPrivateDarkenScreenFunction() override {}
+  ResponseAction Run() override;
+  DECLARE_EXTENSION_FUNCTION("accessibilityPrivate.darkenScreen",
+                             ACCESSIBILITY_PRIVATE_DARKENSCREEN)
+};
+
 #endif  // CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_EXTENSION_API_H_