Wire up an api to darken screen for accessibility

chrome/common/extensions/api/automation_internal.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.
 
 // This is the implementation layer of the chrome.automation API, and is
 // essentially a translation of the internal accessibility tree update system
 // into an extension API.
 namespace automationInternal {
   // Data for an accessibility event and/or an atomic change to an accessibility
   // tree. See ui/accessibility/ax_tree_update.h for an extended explanation of
@@ skipping 22 matching lines @@
     doDefault,
     getImageData,
     makeVisible,
     resumeMedia,
     setAccessibilityFocus,
     setSequentialFocusNavigationStartingPoint,
     setSelection,
     startDuckingMedia,
     stopDuckingMedia,
     suspendMedia,
-    showContextMenu
+    showContextMenu,
+    toggleDarkenScreen
   };
 
   // Arguments required for all actions supplied to performAction.
   dictionary PerformActionRequiredParams {
     long treeID;
     long automationNodeID;
     ActionType actionType;
   };
 
   // Arguments for the setSelection action supplied to performAction.
@@ skipping 17 matching lines @@
     long routingID;
     long? tabID;
   };
 
   // Arguments for the getImageData function.
   dictionary GetImageDataParams {
     long maxWidth;
     long maxHeight;
   };
 
+  // Arguments for the toggleDarkenScreen action supplied to performAction.
+  dictionary ToggleDarkenScreenParams {
+    // Whether to darken or undarken screen.
+    boolean darkenScreen;

[dmazzoni, 2017/03/22 21:40:48]

Passing a bool doesn't really match "toggle". How about calling the
action setScreenDarkening instead?

+  };
+
   // Returns the accessibility tree id of the web contents who's accessibility
   // was enabled using enableTab().
   callback EnableTabCallback = void(long tree_id);
 
   // Callback called when enableDesktop() returns.
   callback EnableDesktopCallback = void();
 
   // Callback called when querySelector() returns.
   callback QuerySelectorCallback = void(long resultAutomationNodeID);
 
@@ skipping 31 matching lines @@
                              long nodeID,
                              DOMString changeType);
 
     static void onChildTreeID(long treeID, long nodeID);
 
     static void onNodesRemoved(long treeID, long[] nodeIDs);
 
     static void onAccessibilityTreeSerializationError(long treeID);
   };
 };