win vs2015: fix variable shadowing warnings

net/base/mime_util.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 <algorithm>
 #include <iterator>
 #include <map>
 #include <string>
 
 #include "base/containers/hash_tables.h"
@@ skipping 1257 matching lines @@
   { "audio/", kStandardAudioTypes, arraysize(kStandardAudioTypes) },
   { "video/", kStandardVideoTypes, arraysize(kStandardVideoTypes) },
   { NULL, NULL, 0 }
 };
 
 void GetExtensionsFromHardCodedMappings(
     const MimeInfo* mappings,
     size_t mappings_len,
     const std::string& leading_mime_type,
     base::hash_set<base::FilePath::StringType>* extensions) {
-  base::FilePath::StringType extension;
   for (size_t i = 0; i < mappings_len; ++i) {
     if (StartsWithASCII(mappings[i].mime_type, leading_mime_type, false)) {
       std::vector<string> this_extensions;
       base::SplitString(mappings[i].extensions, ',', &this_extensions);
       for (size_t j = 0; j < this_extensions.size(); ++j) {
 #if defined(OS_WIN)
         base::FilePath::StringType extension(
             base::UTF8ToWide(this_extensions[j]));
 #else
         base::FilePath::StringType extension(this_extensions[j]);
@@ skipping 129 matching lines @@
   post_data->append("\r\n" + value + "\r\n");
 }
 
 void AddMultipartFinalDelimiterForUpload(const std::string& mime_boundary,
                                          std::string* post_data) {
   DCHECK(post_data);
   post_data->append("--" + mime_boundary + "--\r\n");
 }
 
 }  // namespace net