Run clang-modernize -use-nullptr over src/extensions/.

extensions/common/features/json_feature_provider_source.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 "extensions/common/features/json_feature_provider_source.h"
 
 #include "base/json/json_reader.h"
 #include "base/logging.h"
 #include "ui/base/resource/resource_bundle.h"
 
@@ skipping 22 matching lines @@
     value_as_dict.reset(static_cast<base::DictionaryValue*>(value.release()));
   } else {
     // There was some error loading the features file.
     // http://crbug.com/176381
     value_as_dict.reset(new base::DictionaryValue());
   }
 
   // Ensure there are no key collisions.
   for (base::DictionaryValue::Iterator iter(*value_as_dict); !iter.IsAtEnd();
        iter.Advance()) {
-    if (dictionary_.GetWithoutPathExpansion(iter.key(), NULL))
+    if (dictionary_.GetWithoutPathExpansion(iter.key(), nullptr))
       LOG(FATAL) << "Key " << iter.key() << " is defined in " << name_
                  << " JSON feature files more than once.";
   }
 
   // Merge.
   dictionary_.MergeDictionary(value_as_dict.get());
 }
 
 }  // namespace extensions