Update from https://crrev.com/315085

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 341 matching lines @@
   // MPEG-4.
   "video/mp4",
   "video/x-m4v",
   "audio/mp4",
   "audio/x-m4a",
 
   // MP3.
   "audio/mp3",
   "audio/x-mp3",
   "audio/mpeg",
+  "audio/aac",
 
 #if defined(ENABLE_MPEG2TS_STREAM_PARSER)
   // MPEG-2 TS.
   "video/mp2t",
 #endif
 };
 
 // Note:
 // - does not include javascript types list (see supported_javascript_types)
 // - does not include types starting with "text/" (see
@@ skipping 1007 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