Enable pinch-zoom on the new login page.

extensions/common/api/web_view_internal.json

 // Copyright 2014 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": "webViewInternal",
     "description": "none",
     "compiler_options": {
       "implemented_in": "extensions/browser/api/web_view/web_view_internal_api.h"
@@ skipping 352 matching lines @@
             "type": "integer",
             "name": "instanceId"
           },
           {
             "type": "boolean",
             "name": "allow"
           }
         ]
       },
       {
+        "name": "setAllowScaling",
+        "type": "function",
+        "parameters": [
+          {
+            "type": "integer",
+            "name": "instanceId"
+          },
+          {
+            "type": "boolean",
+            "name": "allow"
+          }
+        ]
+      },
+      {
         "name": "setName",
         "type": "function",
         "parameters": [
           {
             "type": "integer",
             "name": "instanceId"
           },
           {
             "type": "string",
             "name": "frameName"
@@ skipping 93 matching lines @@
             "type": "function",
             "description": "Called when deletion has completed.",
             "optional": true,
             "parameters": []
           }
         ]
       }
     ]
   }
 ]