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

ios/web/webui/web_ui_ios_impl.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.
 
 #include "ios/web/webui/web_ui_ios_impl.h"
 
 #include "base/json/json_writer.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "ios/public/provider/web/web_ui_ios_controller.h"
 #include "ios/public/provider/web/web_ui_ios_controller_factory.h"
 #include "ios/public/provider/web/web_ui_ios_message_handler.h"
 #include "ios/web/web_state/web_state_impl.h"
 
 using web::WebUIIOSController;
 
 namespace web {
 
 // static
 base::string16 WebUIIOS::GetJavascriptCall(
     const std::string& function_name,
     const std::vector<const base::Value*>& arg_list) {
   base::string16 parameters;
   std::string json;
   for (size_t i = 0; i < arg_list.size(); ++i) {
     if (i > 0)
       parameters += base::char16(',');
 
-    base::JSONWriter::Write(arg_list[i], &json);
+    base::JSONWriter::Write(*arg_list[i], &json);
     parameters += base::UTF8ToUTF16(json);
   }
   return base::ASCIIToUTF16(function_name) + base::char16('(') + parameters +
          base::char16(')') + base::char16(';');
 }
 
 WebUIIOSImpl::WebUIIOSImpl(WebStateImpl* web_state) : web_state_(web_state) {
   DCHECK(web_state);
 }
 
@@ skipping 101 matching lines @@
   handler->set_web_ui(this);
   handler->RegisterMessages();
   handlers_.push_back(handler);
 }
 
 void WebUIIOSImpl::ExecuteJavascript(const base::string16& javascript) {
   web_state_->ExecuteJavaScriptAsync(javascript);
 }
 
 }  // namespace web