Implement virtual keyboard hiding.

chrome/common/extensions/api/virtual_keyboard_private.json

 // Copyright 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.
 
 [
   {
     "namespace": "virtualKeyboardPrivate",
     "platforms": ["chromeos"],
     "description": "none",
     "types": [
@@ skipping 27 matching lines @@
         ]
       },
       {
         "name": "moveCursor",
         "type": "function",
         "description": "Move cursor on the current focused textfield by swipe.",
         "parameters": [
           { "name": "swipe_direction",
             "type": "integer",
             "discription": "The direction of the cursor movement."
-          },
+          },
           { "name": "modifier_flags",
             "type": "integer",
             "description": "Bitmask representing the state of the system modifier keys."
           },
           { "type": "function",
             "name": "callback",
             "optional": true,
             "decription": "called when the swipe movement is completed.",
             "parameters": []
           }
-        ]
+        ]
       },
       {
         "name": "sendKeyEvent",
         "type": "function",
         "description": "Sends a fabricated key event to the focused input field.",
         "parameters": [
           { "name": "keyEvent",
             "$ref": "VirtualKeyboardEvent",
             "description": ""
           },
           { "name": "callback",
             "type": "function",
             "optional": true,
             "description": "Called after processing the event.",
             "parameters": []
           }
         ]
+      },
+      {
+        "name": "hideKeyboard",
+        "type": "function",
+        "description": "Hides the virtual keyboard.",
+        "parameters": [
+          { "type": "function",
+            "name": "callback",
+            "optional": true,
+            "description": "Called when the keyboard is hidden.",
+            "parameters": []
+          }
+        ]
       }
     ]
   }
 ]