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

content/public/browser/download_item.h

 // Copyright (c) 2011 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.
 //
 // Each download is represented by a DownloadItem, and all DownloadItems
 // are owned by the DownloadManager which maintains a global list of all
 // downloads. DownloadItems are created when a user initiates a download,
 // and exist for the duration of the browser life time.
 //
 // Download observers:
@@ skipping 246 matching lines @@
   virtual const FilePath& GetFullPath() const = 0;
   virtual void SetPathUniquifier(int uniquifier) = 0;
   virtual const GURL& GetURL() const = 0;
   virtual const std::vector<GURL>& GetUrlChain() const = 0;
   virtual const GURL& GetOriginalUrl() const = 0;
   virtual const GURL& GetReferrerUrl() const = 0;
   virtual std::string GetSuggestedFilename() const = 0;
   virtual std::string GetContentDisposition() const = 0;
   virtual std::string GetMimeType() const = 0;
   virtual std::string GetOriginalMimeType() const = 0;
-  virtual std::string GetReferrerCharset() const = 0;
+  virtual std::string GetDefaultCharset() const = 0;
   virtual std::string GetRemoteAddress() const = 0;
   virtual int64 GetTotalBytes() const = 0;
   virtual void SetTotalBytes(int64 total_bytes) = 0;
   virtual int64 GetReceivedBytes() const = 0;
   virtual const std::string& GetHashState() const = 0;
   virtual int32 GetId() const = 0;
   virtual DownloadId GetGlobalId() const = 0;
   virtual base::Time GetStartTime() const = 0;
   virtual base::Time GetEndTime() const = 0;
   virtual void SetDbHandle(int64 handle) = 0;
@@ skipping 67 matching lines @@
   virtual void SetExternalData(const void* key, ExternalData* data) = 0;
 
   virtual std::string DebugString(bool verbose) const = 0;
 
   virtual void MockDownloadOpenForTesting() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DOWNLOAD_ITEM_H_