Add hook for extension to check sync status.

chrome/common/extensions/api/preferences_private.json

Index: chrome/common/extensions/api/preferences_private.json
diff --git a/chrome/common/extensions/api/preferences_private.json b/chrome/common/extensions/api/preferences_private.json
index 4ceeb5fafe3b011aeb4f0658da0b6b3f70b4bd66..c7a146f815e758f59c7ac55a3541003b95600fb3 100644
--- a/chrome/common/extensions/api/preferences_private.json
+++ b/chrome/common/extensions/api/preferences_private.json
@@ -12,6 +12,26 @@
         "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",
+        "type": "function",
+        "parameters": [
+          {
+            "name": "callback",
+            "type": "function",
+            "parameters": [
+              {
+                "name": "categories",
+                "type": "array",
+                "items": {"type": "string"}
+              }
+            ]
+          }
+        ]
+      }
+    ]
   }
 ]