DRAFT: Add setKeyboardVisibility API.

ui/keyboard/resources/api_adapter.js

 // Copyright (c) 2013 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.
 
 function logIfError() {
   if (chrome.runtime.lastError) {
     console.log(chrome.runtime.lastError);
   }
 }
 
 function sendKeyEvent(keyEvent) {
   keyEvent.type = 'keydown';
   chrome.experimental.input.virtualKeyboard.sendKeyboardEvent(keyEvent,
       logIfError);
   keyEvent.type = 'keyup';
   chrome.experimental.input.virtualKeyboard.sendKeyboardEvent(keyEvent,
       logIfError);
 }
+
+var setKeyboardVisibility =
+    chrome.experimental.input.virtualKeyboard.setKeyboardVisibility;