referrer_charset is a lie. It's really the user's default_charset.

content/browser/download/download_manager_impl.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 "content/browser/download/download_manager_impl.h"
 
 #include <iterator>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 815 matching lines @@
   // The null times make the date range unbounded.
   return RemoveDownloadsBetween(base::Time(), base::Time());
 }
 
 // Initiate a download of a specific URL. We send the request to the
 // ResourceDispatcherHost, and let it send us responses like a regular
 // download.
 void DownloadManagerImpl::DownloadUrl(
     const GURL& url,
     const GURL& referrer,
-    const std::string& referrer_charset,
+    const std::string& default_charset,
     bool prefer_cache,
     const DownloadSaveInfo& save_info,
     WebContents* web_contents) {
   ResourceDispatcherHost* resource_dispatcher_host =
       ResourceDispatcherHost::Get();
 
   // We send a pointer to content::ResourceContext, instead of the usual
   // reference, so that a copy of the object isn't made.
   // base::Bind can't handle 7 args, so we use URLParams and RenderParams.
   BrowserThread::PostTask(
@@ skipping 360 matching lines @@
        it != history_downloads_.end(); ++it) {
     if (it->second->IsComplete() && !it->second->GetOpened())
       ++num_unopened;
   }
   download_stats::RecordOpensOutstanding(num_unopened);
 }
 
 void DownloadManagerImpl::SetFileManager(DownloadFileManager* file_manager) {
   file_manager_ = file_manager;
 }