[Sync] Replacing NULL with nullptr/null throughout sync code.

components/browser_sync/profile_sync_service_typed_url_unittest.cc

 // Copyright (c) 2012 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.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 106 matching lines @@
     DCHECK(task_runner.get());
     task_runner_ = task_runner;
   }
 
   void set_backend(scoped_refptr<history::HistoryBackend> backend) {
     backend_ = backend;
   }
 
  private:
   void RunTaskOnDBThread(history::HistoryDBTask* task) {
-    EXPECT_TRUE(task->RunOnDBThread(backend_.get(), NULL));
+    EXPECT_TRUE(task->RunOnDBThread(backend_.get(), nullptr));
   }
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   scoped_refptr<history::HistoryBackend> backend_;
 };
 
 class TestTypedUrlSyncableService : public TypedUrlSyncableService {
   // TODO(gangwu): remove TestProfileSyncService or even remove whole test
   // suite, and make sure typed_url_syncable_service_unittest.cc and the various
   // typed url integration tests.
@@ skipping 908 matching lines @@
   SendNotificationURLsModified(changed_urls);
 
   history::URLRows new_sync_entries;
   GetTypedUrlsFromSyncDB(&new_sync_entries);
 
   // The change should be ignored.
   ASSERT_EQ(0U, new_sync_entries.size());
 }
 
 }  // namespace browser_sync