Re-land: Rename experimental.accessibility to accessibilityPrivate

chrome/browser/resources/chromeos/chromevox/manifest_guest.json

 {
   // NOTE: Keep two json files in this directory in sync. The only difference
   // should be incognito:split in Guest mode version.
   "key": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDltVl1k15pjRzuZfMc3B69inxwm2bZeZ2O8/zFO+NluHnBm3GJ3fzdOoFGJd+M16I8p7zxxQyHeDMfWYASyCeB8XnUEDKjqNLQfCnncsANzHsYoEbYj2nEUML2P13b9q+AAvpCBpAJ4cZp81e9n1y/vbSXHE4385cgkKueItzikQIDAQAB",
   "manifest_version": 2,
   "name": "ChromeVox",
   "version": "1.0",
   "description": "ChromeVox - Giving Voice to Chrome.",
   "incognito": "split",
   "background": {
     "page": "chromevox/background/background.html"
   },
   "permissions": [
+    "accessibilityPrivate",
+    "automation",
     "bookmarks",
     "tabs",
     "experimental",
     "history",
     "tts",
     "systemPrivate",
     "brailleDisplayPrivate",
     "commandLinePrivate",
     "<all_urls>"
   ],
   "content_scripts": [
     {
       "matches": [ "<all_urls>" ],
       "exclude_globs": [ "chrome-extension://mndnfokpggljbaajbnioimlmbfngpief/chromevox/background/background.html" ],
       "all_frames": true,
       "js": [
         "chromeVoxChromePageScript.js"
       ]
     }
   ],
   "web_accessible_resources": [
     "chromevox/injected/api.js",
     "chromevox/injected/api_util.js",
     "chromevox/injected/mathjax.js",
     "chromevox/injected/mathjax_external_util.js"
   ],
   "default_locale": "en"
 }