[Offline pages] Refactor URL conversions from TabAndroid

components/offline_pages/offline_page_test_store.cc

Index: components/offline_pages/offline_page_test_store.cc
diff --git a/components/offline_pages/offline_page_test_store.cc b/components/offline_pages/offline_page_test_store.cc
index 755191ce2b70565b5c773cdc999454b0e5833b36..8c8ea9438e09953cd41e6b3488395cd6cd6535b4 100644
--- a/components/offline_pages/offline_page_test_store.cc
+++ b/components/offline_pages/offline_page_test_store.cc
@@ -41,7 +41,8 @@ void OfflinePageTestStore::AddOrUpdateOfflinePage(
   bool result = scenario_ != TestScenario::WRITE_FAILED;
   if (result)
     offline_pages_[offline_page.bookmark_id] = offline_page;
-  task_runner_->PostTask(FROM_HERE, base::Bind(callback, result));
+  if (!callback.is_null())
+    task_runner_->PostTask(FROM_HERE, base::Bind(callback, result));
 }
 
 void OfflinePageTestStore::RemoveOfflinePages(