Don't SyzyASan-instrument content_shell if 'syzyasan' isn't defined.

content/content_shell.gypi

 # 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': {
     'content_shell_product_name': 'Content Shell',
     # The "19" is so that sites that sniff for version think that this is
     # something reasonably current; the "77.34.5" is a hint that this isn't a
     # standard Chrome.
@@ skipping 1053 matching lines @@
             'shell/tools/content_shell_crash_service.cc',
           ],
           'msvs_settings': {
             'VCLinkerTool': {
               'SubSystem': '2',         # Set /SUBSYSTEM:WINDOWS
             },
           },
         },
       ],
     }],  # OS=="win"
-    ['OS=="win" and fastbuild==0 and target_arch=="ia32"', {
+    ['OS=="win" and fastbuild==0 and target_arch=="ia32" and syzyasan==1', {
       'variables': {
         'dest_dir': '<(PRODUCT_DIR)/syzygy',
       },
       'targets': [
         {
           'target_name': 'content_shell_syzyasan',
           'type': 'none',
           'sources' : [],
           # Instrument content_shell with SyzyAsan.
           'actions': [
@@ skipping 14 matching lines @@
                 '--input_symbol', '<(PRODUCT_DIR)/content_shell.exe.pdb',
                 '--destination_dir', '<(dest_dir)',
               ],
             },
           ],
         },
       ],
     }],  # OS=="win" and fastbuild==0 and target_arch=="ia32"
   ]
 }