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

net/base/net_util_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 "net/base/net_util.h"
 
 #include <string.h>
 
 #include <algorithm>
 
@@ skipping 27 matching lines @@
 };
 
 struct HeaderParamCase {
   const char* header_name;
   const char* param_name;
   const char* expected;
 };
 
 struct FileNameCDCase {
   const char* header_field;
-  const char* referrer_charset;
+  const char* default_charset;
   const wchar_t* expected;
 };
 
 const char* kLanguages[] = {
   "",      "en",    "zh-CN",    "ja",    "ko",
   "he",    "ar",    "ru",       "el",    "fr",
   "de",    "pt",    "sv",       "th",    "hi",
   "de,en", "el,en", "zh-TW,en", "ko,ja", "he,ru,en",
   "zh,ru,en"
 };
@@ skipping 321 matching lines @@
 
 struct CompliantHostCase {
   const char* host;
   const char* desired_tld;
   bool expected_output;
 };
 
 struct GenerateFilenameCase {
   const char* url;
   const char* content_disp_header;
-  const char* referrer_charset;
+  const char* default_charset;
   const char* suggested_filename;
   const char* mime_type;
   const wchar_t* default_filename;
   const wchar_t* expected_filename;
 };
 
 struct UrlTestData {
   const char* description;
   const char* input;
   const char* languages;
@@ skipping 108 matching lines @@
   }
   return out;
 }
 
 void RunGenerateFileNameTestCase(const GenerateFilenameCase* test_case,
                                  size_t iteration,
                                  const char* suite) {
   std::string default_filename(WideToUTF8(test_case->default_filename));
   FilePath file_path = GenerateFileName(
       GURL(test_case->url), test_case->content_disp_header,
-      test_case->referrer_charset, test_case->suggested_filename,
+      test_case->default_charset, test_case->suggested_filename,
       test_case->mime_type, default_filename);
   EXPECT_EQ(test_case->expected_filename,
             file_util::FilePathAsWString(file_path))
       << "Iteration " << iteration << " of " << suite << ": " << test_case->url;
 }
 
 }  // anonymous namespace
 
 TEST(NetUtilTest, FileURLConversion) {
   // a list of test file names and the corresponding URLs
@@ skipping 1554 matching lines @@
   };
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(selection_tests); ++i)
     RunGenerateFileNameTestCase(&selection_tests[i], i, "selection");
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(generation_tests); ++i)
     RunGenerateFileNameTestCase(&generation_tests[i], i, "generation");
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(generation_tests); ++i) {
     GenerateFilenameCase test_case = generation_tests[i];
-    test_case.referrer_charset = "GBK";
+    test_case.default_charset = "GBK";
     RunGenerateFileNameTestCase(&test_case, i, "generation (referrer=GBK)");
   }
 }
 
 // This is currently a windows specific function.
 #if defined(OS_WIN)
 namespace {
 
 struct GetDirectoryListingEntryCase {
   const wchar_t* name;
@@ skipping 1099 matching lines @@
       if (it->address[i] != 0) {
         all_zeroes = false;
         break;
       }
     }
     EXPECT_FALSE(all_zeroes);
   }
 }
 
 }  // namespace net