Add a build arg to control whether to use a jessie sysroot.

tools/mb/mb_config.pyl

 # Copyright 2015 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.
 
 # This is a .pyl, or "Python Literal", file. You can treat it just like a
 # .json file, with the following exceptions:
 # * all keys must be quoted (use single quotes, please);
 # * comments are allowed, using '#' syntax; and
 # * trailing commas are allowed.
 
@@ skipping 1791 matching lines @@
     },
 
     'ozone': {
       'gn_args': 'use_ozone=true',
     },
 
     'ozone_linux': {
       'gn_args': ('ozone_auto_platforms=false ozone_platform_wayland=true '
                   'ozone_platform_x11=true ozone_platform_gbm=true '
                   'enable_package_mash_services=true use_ash=false '
-                  'use_xkbcommon=true'),
+                  'use_jessie_sysroot=true use_xkbcommon=true'),
     },
 
     'pdf_xfa': {
       'gn_args': 'pdf_enable_xfa=true',
     },
 
     # Note: This is probably not what you want to use. Instead use one of the
     # chrome_with_codecs or chromeos_with_codecs mixins.
     'proprietary_codecs': {
       'gn_args': 'proprietary_codecs=true',
@@ skipping 77 matching lines @@
 
     'x64': {
       'gn_args': 'target_cpu="x64"',
     },
 
     'x86': {
       'gn_args': 'target_cpu="x86"',
     },
   },
 }