Wire up an api to darken screen for accessibility

chrome/common/extensions/api/automation.idl

 // Copyright 2014 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.
 
 // The <code>chrome.automation</code> API allows developers to access the
 // automation (accessibility) tree for the browser. The tree resembles the DOM
 // tree, but only exposes the <em>semantic</em> structure of a page. It can be
 // used to programmatically interact with a page by examining names, roles, and
 // states, listening for events, and performing actions on nodes.
 [nocompile] namespace automation {
@@ skipping 688 matching lines @@
 
     // Start ducking any media within this tree.
     static void startDuckingMedia();
 
     // Stop ducking any media within this tree.
     static void stopDuckingMedia();
 
     // Suspend any media playing within this tree.
     static void suspendMedia();
 
+    // Darkens (or undarkens) the screen.
+    static void toggleDarkenScreen(boolean toggle);
+
     // Adds a listener for the given event type and event phase.
     static void addEventListener(
         EventType eventType, AutomationListener listener, boolean capture);
 
     // Removes a listener for the given event type and event phase.
     static void removeEventListener(
         EventType eventType, AutomationListener listener, boolean capture);
 
     // Gets the first node in this node's subtree which matches the given CSS
     // selector and is within the same DOM context.
@@ skipping 61 matching lines @@
     // Everything in the tree between the two node/offset pairs gets included
     // in the selection. The anchor is where the user started the selection,
     // while the focus is the point at which the selection gets extended
     // e.g. when dragging with a mouse or using the keyboard. For nodes with
     // the role staticText, the offset gives the character offset within
     // the value where the selection starts or ends, respectively.
     [nocompile] static void setDocumentSelection(
         SetDocumentSelectionParams params);
   };
 };