Add private API to notify end of initialization.

chrome/common/extensions/api/input_method_private.json

 // Copyright (c) 2012 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": "inputMethodPrivate",
     "nodoc": true,
     "platforms": ["chromeos"],
     "types": [],
@@ skipping 10 matching lines @@
             "description": "Callback which is called with the current input method.",
             "parameters": [
               {
                 "name": "inputMethodId",
                 "type": "string",
                 "description": "Current input method."
               }
             ]
           }
         ]
+      }, {
+        "name": "startIme",
+        "type": "function",
+        "description": "Notify to input method engine to be ready to accept events.",
+        "parameters" : []
       }
     ],
     "events": [
       {
         "name": "onChanged",
         "type": "function",
         "description": "Fired when the input method is changed.",
         "parameters": [
           {
             "name": "newInputMethodId",
             "type": "string",
             "description": "New input method which is being used."
           }
         ]
       }
     ]
   }
 ]