revert r49217, which caused unit test failures on win:

net/base/net_util.cc

 // Copyright (c) 2010 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 <algorithm>
 #include <map>
 #include <unicode/ucnv.h>
 #include <unicode/uidna.h>
@@ skipping 1063 matching lines @@
       FILE_PATH_LITERAL("download");
 
   // about: and data: URLs don't have file names, but esp. data: URLs may
   // contain parts that look like ones (i.e., contain a slash).
   // Therefore we don't attempt to divine a file name out of them.
   if (url.SchemeIs("about") || url.SchemeIs("data")) {
     return default_name.empty() ? FilePath(kFinalFallbackName) : default_name;
   }
 
   const std::string filename_from_cd = GetFileNameFromCD(content_disposition,
-                                                         referrer_charset);
+                                                          referrer_charset);
 #if defined(OS_WIN)
   FilePath::StringType filename = UTF8ToWide(filename_from_cd);
 #elif defined(OS_POSIX)
   FilePath::StringType filename = filename_from_cd;
 #endif
 
   if (!filename.empty()) {
     // Remove any path information the server may have sent, take the name
     // only.
     filename = FilePath(filename).BaseName().value();
 
     // Next, remove "." from the beginning and end of the file name to avoid
     // tricks with hidden files, "..", and "."
     TrimString(filename, FILE_PATH_LITERAL("."), &filename);
   }
   if (filename.empty()) {
     if (url.is_valid()) {
       const std::string unescaped_url_filename = UnescapeURLComponent(
           url.ExtractFileName(),
           UnescapeRule::SPACES | UnescapeRule::URL_SPECIAL_CHARS);
-
-      // The URL should be escaped UTF-8, but may not be.
-      std::string decoded_filename;
-      bool ignore;
-      DecodeWord(unescaped_url_filename, referrer_charset, &ignore,
-                 &decoded_filename);
-
 #if defined(OS_WIN)
-      filename = UTF8ToWide(decoded_filename);
+      filename = UTF8ToWide(unescaped_url_filename);
 #elif defined(OS_POSIX)
-      filename = decoded_filename;
+      filename = unescaped_url_filename;
 #endif
     }
   }
 
 #if defined(OS_WIN)
   { // Handle CreateFile() stripping trailing dots and spaces on filenames
     // http://support.microsoft.com/kb/115827
     std::string::size_type pos = filename.find_last_not_of(L" .");
     if (pos == std::string::npos)
       filename.resize(0);
@@ skipping 741 matching lines @@
     unsigned char mask = 0xFF << (8 - remaining_bits);
     int i = num_entire_bytes_in_prefix;
     if ((ip_number[i] & mask) != (ip_prefix[i] & mask))
       return false;
   }
 
   return true;
 }
 
 }  // namespace net