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

chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service_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/bind.h"
 #include "base/json/json_writer.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.h"
@@ skipping 51 matching lines @@
     const std::string& message) {
   return syncer::SyncError(location, SyncError::DATATYPE_ERROR, message, type_);
 }
 
 // Convenience method to allow us to use EXPECT_EQ to compare values.
 std::string ToJson(const Value* value) {
   if (!value)
     return std::string();
 
   std::string json_value;
-  base::JSONWriter::Write(value, &json_value);
+  base::JSONWriter::Write(*value, &json_value);
   return json_value;
 }
 
 }  // namespace
 
 class SupervisedUserSharedSettingsServiceTest : public ::testing::Test {
  protected:
   typedef base::CallbackList<void(const std::string&, const std::string&)>
       CallbackList;
 
@@ skipping 182 matching lines @@
       settings_service_.GetAllSyncData(SUPERVISED_USER_SHARED_SETTINGS).size());
   EXPECT_EQ(ToJson(&name),
             ToJson(settings_service_.GetValue(kIdA, "name")));
   EXPECT_EQ(ToJson(&age), ToJson(settings_service_.GetValue(kIdA, "age")));
   EXPECT_EQ(ToJson(&bar), ToJson(settings_service_.GetValue(kIdB, "foo")));
   EXPECT_EQ(ToJson(&blurp), ToJson(settings_service_.GetValue(kIdC, "baz")));
   EXPECT_FALSE(settings_service_.GetValue(kIdA, "foo"));
   EXPECT_FALSE(settings_service_.GetValue(kIdB, "name"));
   EXPECT_FALSE(settings_service_.GetValue(kIdC, "name"));
 }