Wire up an api to darken screen for accessibility

chrome/browser/resources/chromeos/chromevox/cvox2/background/braille_command_handler.js

 // Copyright 2016 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.
 
 /**
  * @fileoverview ChromeVox braille commands.
  */
 
 goog.provide('BrailleCommandHandler');
 
@@ skipping 116 matching lines @@
   map([1, 2, 4, 7], 'previousFormField');
   map([1, 2, 5, 7], 'previousHeading');
   map([4, 5, 7], 'previousLink');
   map([2, 3, 4, 5, 7], 'previousTable');
 
   map([8], 'forceClickOnCurrentItem');
   map([3, 4], 'toggleSearchWidget');
 
   // Question.
   map([1, 4, 5, 6], 'toggleKeyboardHelp');
+
+  // All cells (with 7 as mod).
+  map([1, 2, 3, 4, 5, 6, 7], 'darkenScreen');
+  map([1, 2, 3, 4, 5, 6], 'undarkenScreen');
 };
 
 BrailleCommandHandler.init_();
 
 }); //  goog.scope