Add hook for extension to check sync status.

chrome/common/extensions/api/preferences_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": "preferencesPrivate",
     "description": "none",
     "properties": {
       "googleGeolocationAccessEnabled": {
+        "nocompile": true,
         "$ref": "types.private.ChromeDirectSetting",
         "value": ["googlegeolocationaccess.enabled", {"type":"boolean"}],
         "description": "If enabled, Google services can access the user's location. This preference's value is a boolean, defaulting to <code>false</code>."
       }
-    }
+    },
+    "functions": [
+      {
+        "name": "getSyncCategoriesWithoutPassphrase",
+        "description": "Returns a list of sync categories the user has enabled without using a custom passphrase for encryption",

[Jeffrey Yasskin, 2013/12/19 23:47:24]

Please document the list of possible category strings here, or say where in the
source the list is defined. These files are where we need to be able to look to
learn the contract for any new API.

+        "type": "function",
+        "parameters": [
+          {
+            "name": "callback",
+            "type": "function",
+            "parameters": [
+              {
+                "name": "categories",
+                "type": "array",
+                "items": {"type": "string"}
+              }
+            ]
+          }
+        ]
+      }
+    ]
   }
 ]