Convert JsonWriter::Write to taking a const ref for the in-param

extensions/browser/value_store/value_store_change.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/browser/value_store/value_store_change.h"
 
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 
 // static
 std::string ValueStoreChange::ToJson(
     const ValueStoreChangeList& changes) {
   base::DictionaryValue changes_value;
   for (ValueStoreChangeList::const_iterator it = changes.begin();
       it != changes.end(); ++it) {
     base::DictionaryValue* change_value = new base::DictionaryValue();
     if (it->old_value()) {
       change_value->Set("oldValue", it->old_value()->DeepCopy());
     }
     if (it->new_value()) {
       change_value->Set("newValue", it->new_value()->DeepCopy());
     }
     changes_value.SetWithoutPathExpansion(it->key(), change_value);
   }
   std::string json;
-  base::JSONWriter::Write(&changes_value, &json);
+  base::JSONWriter::Write(changes_value, &json);
   return json;
 }
 
 ValueStoreChange::ValueStoreChange(
     const std::string& key, base::Value* old_value, base::Value* new_value)
     : inner_(new Inner(key, old_value, new_value)) {}
 
 ValueStoreChange::~ValueStoreChange() {}
 
 const std::string& ValueStoreChange::key() const {
   DCHECK(inner_.get());
   return inner_->key_;
 }
 
 const base::Value* ValueStoreChange::old_value() const {
   DCHECK(inner_.get());
   return inner_->old_value_.get();
 }
 
 const base::Value* ValueStoreChange::new_value() const {
   DCHECK(inner_.get());
   return inner_->new_value_.get();
 }
 
 ValueStoreChange::Inner::Inner(
     const std::string& key, base::Value* old_value, base::Value* new_value)
     : key_(key), old_value_(old_value), new_value_(new_value) {}
 
 ValueStoreChange::Inner::~Inner() {}