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

chrome/browser/supervised_user/experimental/supervised_user_async_url_checker_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 <string>
 
 #include "base/callback.h"
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 35 matching lines @@
                                                   result_count);
   dict.SetWithoutPathExpansion("searchInformation", search_info_dict);
   if (result_count != "0") {
     base::ListValue* results_list = new base::ListValue;
     base::DictionaryValue* result_dict = new base::DictionaryValue;
     result_dict->SetStringWithoutPathExpansion("link", url.spec());
     results_list->Append(result_dict);
     dict.SetWithoutPathExpansion("items", results_list);
   }
   std::string result;
-  base::JSONWriter::Write(&dict, &result);
+  base::JSONWriter::Write(dict, &result);
   return result;
 }
 
 }  // namespace
 
 class SupervisedUserAsyncURLCheckerTest : public testing::Test {
  public:
   SupervisedUserAsyncURLCheckerTest()
       : next_url_(0),
         request_context_(new net::TestURLRequestContextGetter(
@@ skipping 155 matching lines @@
 TEST_F(SupervisedUserAsyncURLCheckerTest, CoalesceRequestsToSameURL) {
   GURL url(GetNewURL());
   // Start two checks for the same URL.
   EXPECT_FALSE(CheckURL(url));
   EXPECT_FALSE(CheckURL(url));
   // A single response should answer both checks.
   EXPECT_CALL(*this, OnCheckDone(url, SupervisedUserURLFilter::ALLOW, false))
       .Times(2);
   SendValidResponse(true, url);
 }