[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/driver/shared_change_processor_unittest.cc

 // Copyright 2014 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 "components/sync/driver/shared_change_processor.h"
 
 #include <cstddef>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 100 matching lines @@
     EXPECT_TRUE(backend_thread_.task_runner()->PostTask(
         FROM_HERE,
         base::Bind(&SyncSharedChangeProcessorTest::TearDownDBSyncableService,
                    base::Unretained(this))));
     // This must happen before the DB thread is stopped since
     // |shared_change_processor_| may post tasks to delete its members
     // on the correct thread.
     //
     // TODO(akalin): Write deterministic tests for the destruction of
     // |shared_change_processor_| on the UI and DB threads.
-    shared_change_processor_ = NULL;
+    shared_change_processor_ = nullptr;
     backend_thread_.Stop();
 
     // Note: Stop() joins the threads, and that barrier prevents this read
     // from being moved (e.g by compiler optimization) in such a way that it
     // would race with the write in ConnectOnDBThread (because by this time,
     // everything that could have run on |backend_thread_| has done so).
     ASSERT_TRUE(did_connect_);
     test_user_share_.TearDown();
   }
 
@@ skipping 92 matching lines @@
 // creates AttachmentService and passes it back to the syncable service.
 TEST_F(SyncSharedChangeProcessorTest, ConnectWithAttachmentStore) {
   SetAttachmentStore();
   Connect();
   EXPECT_TRUE(HasAttachmentService());
 }
 
 }  // namespace
 
 }  // namespace syncer