Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxslt/libxslt.gyp

 # Copyright (c) 2009 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.
 
 {
   'variables': {
     'conditions': [
       ['os_posix == 1 and OS != "mac"', {
         'os_include': 'linux'
       }],
@@ skipping 88 matching lines @@
             '../libxml/libxml.gyp:libxml',
           ],
           'direct_dependent_settings': {
             'defines': [
               'LIBXSLT_STATIC',
             ],
             'include_dirs': [
               '.',
             ],
           },
+          'msvs_disabled_warnings': [
+            # size_t to int conversion.
+            4267,
+          ],
           'variables': {
             'clang_warning_flags': [
               # libxslt stores a char[3] in a `const unsigned char*`.
               '-Wno-pointer-sign',
             ],
           },
           'conditions': [
             ['OS!="win"', {'product_name': 'xslt'}],
           ],
         }],
       ],
     },
   ],
 }