Add virtualKeyboardPrivate API permission to ChromeVox manifest.

This API will be used to send certain keys that are simulated on a braille
display.  These are function keys such as arrow keys, enter, backspace
etc.  The virtual keyboard api is used instead of the similar api in the
IME api so that these keys can be used outside of text fields and
when the Braille IME is not active.

BUG=310285
R=dtseng@chromium.org

Review URL: https://codereview.chromium.org/335063004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278134 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/chromeos/chromevox/manifest.json.jinja2

@@ -25,6 +25,7 @@
     "systemPrivate",
     "brailleDisplayPrivate",
     "commandLinePrivate",
+    "virtualKeyboardPrivate",
     "<all_urls>"
   ],
   "content_scripts": [