Remove base::Value::CreateNullValue

ios/web/web_state/ui/web_view_js_utils.mm

 // 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.
 
 #import "ios/web/web_state/ui/web_view_js_utils.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
@@ skipping 23 matching lines @@
   if (result_type == CFStringGetTypeID()) {
     result.reset(new base::Value(base::SysNSStringToUTF16(wk_result)));
     DCHECK(result->IsType(base::Value::Type::STRING));
   } else if (result_type == CFNumberGetTypeID()) {
     result.reset(new base::Value([wk_result doubleValue]));
     DCHECK(result->IsType(base::Value::Type::DOUBLE));
   } else if (result_type == CFBooleanGetTypeID()) {
     result.reset(new base::Value(static_cast<bool>([wk_result boolValue])));
     DCHECK(result->IsType(base::Value::Type::BOOLEAN));
   } else if (result_type == CFNullGetTypeID()) {
-    result = base::Value::CreateNullValue();
+    result = base::MakeUnique<base::Value>();
     DCHECK(result->IsType(base::Value::Type::NONE));
   } else if (result_type == CFDictionaryGetTypeID()) {
     std::unique_ptr<base::DictionaryValue> dictionary =
         base::MakeUnique<base::DictionaryValue>();
     for (id key in wk_result) {
       NSString* obj_c_string = base::mac::ObjCCast<NSString>(key);
       const std::string path = base::SysNSStringToUTF8(obj_c_string);
       std::unique_ptr<base::Value> value =
           ValueResultFromWKResult(wk_result[obj_c_string], max_depth - 1);
       if (value) {
@@ skipping 42 matching lines @@
                 userInfo:@{NSLocalizedDescriptionKey : error_message}]);
       completion_handler(nil, error);
     });
     return;
   }
 
   [web_view evaluateJavaScript:script completionHandler:completion_handler];
 }
 
 }  // namespace web