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

sync/js/js_event_details.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 "sync/js/js_event_details.h"
 
 #include "base/json/json_writer.h"
 
 namespace syncer {
 
 JsEventDetails::JsEventDetails() {}
 
 JsEventDetails::JsEventDetails(base::DictionaryValue* details)
     : details_(details) {}
 
 JsEventDetails::~JsEventDetails() {}
 
 const base::DictionaryValue& JsEventDetails::Get() const {
   return details_.Get();
 }
 
 std::string JsEventDetails::ToString() const {
   std::string str;
-  base::JSONWriter::Write(&Get(), &str);
+  base::JSONWriter::Write(Get(), &str);
   return str;
 }
 
 }  // namespace syncer