Implement virtual keyboard hiding.

ui/keyboard/resources/webui/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 insertText(text) {
   chrome.send('insertText', [ text ]);
 }
 
 function sendKeyEvent(event) {
   chrome.send('sendKeyEvent', [ event ]);
 }
 
+function hideKeyboard() {
+  chrome.send('hideKeyboard');
+}
+
 (function(exports) {
   /**
    * An array to save callbacks of each request.
    * @type {Array.<function(Object)>}
    */
   var requestIdCallbackMap = [];
 
   /**
    * An incremental integer that represents a unique requestId.
    * @type {number}
@@ skipping 46 matching lines @@
     if (!requestIdCallbackMap[requestId])
       return;
     requestIdCallbackMap[requestId](inputContext);
   }
 
   exports.OnTextInputBoxFocused = OnTextInputBoxFocused;
   exports.getInputContext = GetInputContext;
   exports.cancelRequest = CancelRequest;
   exports.GetInputContextCallback = GetInputContextCallback;
 })(this);