Move allocate instance id to chrome/.

chrome/common/extensions/api/webview.json

 // 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.
 
 [
   {
     "namespace": "webview",
     "description": "none",
     "dependencies": ["contextMenusInternal"],
     "types": [
@@ skipping 642 matching lines @@
             "parameters": [
               {
                 "name": "allowed",
                 "type": "boolean"
               }
             ]
           }
         ]
       },
       {
+        "name": "navigate",
+        "type": "function",
+        "parameters": [
+          {
+            "type": "integer",
+            "name": "instanceId"
+          },
+          {
+            "type": "string",
+            "name": "src"
+          }
+        ]
+      },
+      {
         "name": "showContextMenu",
         "type": "function",
         "parameters": [
           {
             "type": "integer",
             "name": "instanceId",
             "description": "The instance ID of the guest <webview> process. This not exposed to developers through the API."
           },
           {
             "type": "integer",
@@ skipping 34 matching lines @@
       {
         "name": "onClicked",
         "type": "function",
         "nodoc": true,
         "$ref": "contextMenusInternal.onClicked"
       }
     ]
   }
 ]