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

chrome/browser/content_settings/host_content_settings_map_unittest.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 "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/message_loop/message_loop.h"
 #include "base/prefs/pref_service.h"
@@ skipping 702 matching lines @@
 
   // Set punycode equivalent, with different setting.
   scoped_ptr<base::Value> puny_value(base::JSONReader::Read(
       "{\"[*.]xn--ira-ppa.com,*\":{\"images\":2}}"));
   profile.GetPrefs()->Set(
       prefs::kContentSettingsPatternPairs, *puny_value);
 
   // Initialize the content map.
   profile.GetHostContentSettingsMap();
 
-  const base::DictionaryValue* content_setting_prefs =
-      profile.GetPrefs()->GetDictionary(
+  const base::DictionaryValue& content_setting_prefs =
+      *profile.GetPrefs()->GetDictionary(
           prefs::kContentSettingsImagesPatternPairs);
   std::string prefs_as_json;
   base::JSONWriter::Write(content_setting_prefs, &prefs_as_json);
   EXPECT_STREQ("{\"[*.]xn--ira-ppa.com,*\":{\"setting\":2}}",
                prefs_as_json.c_str());
 }
 
 // If a default-content-setting is managed, the managed value should be used
 // instead of the default value.
 TEST_F(HostContentSettingsMapTest, ManagedDefaultContentSetting) {
@@ skipping 347 matching lines @@
       CONTENT_SETTINGS_TYPE_IMAGES, true);
   EXPECT_EQ(CONTENT_SETTING_ALLOW,
             host_content_settings_map->GetContentSetting(
                 host, host, CONTENT_SETTINGS_TYPE_IMAGES, std::string()));
   host_content_settings_map->SetDefaultContentSetting(
       CONTENT_SETTINGS_TYPE_IMAGES, CONTENT_SETTING_BLOCK);
   EXPECT_EQ(CONTENT_SETTING_BLOCK,
             host_content_settings_map->GetContentSetting(
                 host, host, CONTENT_SETTINGS_TYPE_IMAGES, std::string()));
 }