Remove is_win/OS_WIN checks in shell code

shell/filename_util.cc

 // Copyright 2014 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 "shell/filename_util.h"
 
 #include "base/files/file_path.h"
 #include "base/path_service.h"
 #include "base/strings/string_util.h"
 #include "url/gurl.h"
@@ skipping 32 matching lines @@
   // A semicolon is supposed to be some kind of separator according to RFC 2396.
   ReplaceSubstringsAfterOffset(&url_string, 0, FILE_PATH_LITERAL(";"),
                                FILE_PATH_LITERAL("%3B"));
 
   ReplaceSubstringsAfterOffset(&url_string, 0, FILE_PATH_LITERAL("#"),
                                FILE_PATH_LITERAL("%23"));
 
   ReplaceSubstringsAfterOffset(&url_string, 0, FILE_PATH_LITERAL("?"),
                                FILE_PATH_LITERAL("%3F"));
 
-#if defined(OS_POSIX)
   ReplaceSubstringsAfterOffset(&url_string, 0, FILE_PATH_LITERAL("\\"),
                                FILE_PATH_LITERAL("%5C"));
-#endif
 
   return GURL(url_string);
 }
 
 GURL AddTrailingSlashIfNeeded(const GURL& url) {
   if (!url.has_path() || *url.path().rbegin() == '/')
     return url;
 
   std::string path(url.path() + '/');
   GURL::Replacements replacements;
   replacements.SetPathStr(path);
   return url.ReplaceComponents(replacements);
 }
 
 }  // namespace shell
 }  // namespace mojo