Adds new experimental accessibility extension api to enable or disable native accessibility.

chrome/common/extensions/api/experimental_accessibility.json

 // 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.
 
 [
   {
     "namespace": "experimental.accessibility",
     "compiler_options": {
       "implemented_in": "chrome/browser/accessibility/accessibility_extension_api.h"
     },
@@ skipping 136 matching lines @@
         "description": "Enables or disables the accessibility extension api. This must be set to true before event listeners or getFocusedControl will work.",
         "parameters": [
           {
             "type": "boolean",
             "name": "enabled",
             "description": "True if accessibility support should be enabled."
           }
         ]
       },
       {
+        "name": "setNativeAccessibilityEnabled",
+        "type": "function",
+        "description": "Enables or disables native accessibility support. Once disabled, it is up to the calling extension to provide accessibility for web contents.",
+        "parameters": [
+          {
+            "type": "boolean",
+            "name": "enabled",
+            "description": "True if native accessibility support should be enabled."
+          }
+        ]
+      },
+      {
         "name": "getFocusedControl",
         "type": "function",
         "description": "Gets information about the currently focused control.",
         "parameters": [
           {
             "type": "function",
             "name": "callback",
             "parameters": [
               {
                 "name": "control",
@@ skipping 111 matching lines @@
           {
             "$ref": "AccessibilityObject",
             "name": "menu",
             "description": "Information about the menu that was closed."
           }
         ]
       }
     ]
   }
 ]