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

net/http/http_content_disposition_unittest.cc

Index: net/http/http_content_disposition_unittest.cc
===================================================================
--- net/http/http_content_disposition_unittest.cc	(revision 119865)
+++ net/http/http_content_disposition_unittest.cc	(working copy)
@@ -13,7 +13,7 @@
 
 struct FileNameCDCase {
   const char* header;
-  const char* referrer_charset;
+  const char* default_charset;
   const wchar_t* expected;
 };
 
@@ -70,7 +70,7 @@
     {"attachment; filename=\"=?windows-1252?Q?caf=E9?="
      "  =?iso-8859-7?b?4eI=?= .png\"", "", L"caf\x00e9\x03b1\x03b2.png"},
     // Non-ASCII string is passed through and treated as UTF-8 as long as
-    // it's valid as UTF-8 and regardless of |referrer_charset|.
+    // it's valid as UTF-8 and regardless of |default_charset|.
     {"attachment; filename=caf\xc3\xa9.png",
      "iso-8859-1", L"caf\x00e9.png"},
     {"attachment; filename=caf\xc3\xa9.png",
@@ -191,7 +191,7 @@
       L"foo.html"},
   };
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(tests); ++i) {
-    HttpContentDisposition header(tests[i].header, tests[i].referrer_charset);
+    HttpContentDisposition header(tests[i].header, tests[i].default_charset);
     EXPECT_EQ(tests[i].expected,
         UTF8ToWide(header.filename()))
         << "Failed on input: " << tests[i].header;