Fixing remaining VC++ 2015 64-bit build breaks

third_party/libxml/libxml.gyp

 # 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.
 
 {
   'variables': {
     'conditions': [
       # Define an "os_include" variable that points at the OS-specific generated
       # headers.  These were generated by running the configure script offline.
       ['os_posix == 1 and OS != "mac" and OS != "ios"', {
@@ skipping 242 matching lines @@
                 ],
               },
             }],
             # http://www.xmlsoft.org/threads.html says that this is required
             # when using libxml from several threads, which can possibly happen
             # in chrome. On linux, this is picked up by transitivity from
             # pkg-config output from build/linux/system.gyp.
             ['OS=="mac" or OS=="android"', {'defines': ['_REENTRANT']}],
             ['OS=="win"', {
               'product_name': 'libxml2',
-              # Disable unimportant 'unused variable' warning, and
-              # signed/unsigned comparison warning. The signed/unsigned (4101)
-              # is fixed upstream and can be removed eventually.
+              # Disable unimportant 'unused variable' warning.
               # TODO(jschuh): http://crbug.com/167187 size_t -> int
-              'msvs_disabled_warnings': [ 4018, 4101, 4267 ],
+              # TODO(brucedawson): http://crbug.com/554200 fix C4311 warnings
+              # C4311 is a VS 2015 64-bit warning for pointer truncation
+              'msvs_disabled_warnings': [ 4018, 4267, 4311, ],
             }, {  # else: OS!="win"
               'product_name': 'xml2',
             }],
           ],
         }],
         ['OS == "ios"', {
           'toolsets': ['host', 'target'],
         }],
       ],
     },
   ],
 }