[SyncFS] Handle unavailable ExtensionService case.

chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc

Index: chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc
diff --git a/chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc b/chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc
index 24db3cd392d539d1c5a5f9bb2ae7cacdf3b6b64f..1e2ee7a8db4738d7028bd36b8bb986468ec8965d 100644
--- a/chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc
+++ b/chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc
@@ -31,7 +31,10 @@ void ConvertExtensionStatusToDictionary(
     const base::WeakPtr<ExtensionService>& extension_service,
     const base::Callback<void(const base::ListValue&)>& callback,
     const std::map<GURL, std::string>& status_map) {
-  DCHECK(!extension_service);
+  if (!extension_service) {
+    callback.Run(base::ListValue());
+    return;
+  }
 
   base::ListValue list;
   for (std::map<GURL, std::string>::const_iterator itr = status_map.begin();