Make building seccomp-bpf a GYP condition

build/common.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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 1898 matching lines @@
       ['OS=="win" and use_goma==1', {
         # goma doesn't support pch yet.
         'chromium_win_pch': 0,
         # goma doesn't support PDB yet, so win_z7=1 or fastbuild=1.
         'conditions': [
           ['fastbuild==0', {
             'win_z7': 1,
           }],
         ],
       }],
+      # seccomp-bpf is only supportd on three architectures currently.

[Mark Seaborn, 2013/12/18 08:10:21]

Typo: "supported".  Maybe say "seccomp-bpf sandbox" to provide a little more
context.

[jln (very slow on Chromium), 2013/12/19 00:00:19]

Done.

+      # Do not disable seccomp_bpf anywhere without talking to
+      # security@chromium.org!
+      ['((OS=="linux" or OS=="android") and '
+           '(target_arch=="ia32" or target_arch=="x64" or '
+             'target_arch=="arm"))', {
+         'use_seccomp_bpf%': 1,
+      }, {
+         'use_seccomp_bpf%': 0,
+      }]

[Mark Seaborn, 2013/12/18 08:10:21]

Nit: add trailing comma

[jln (very slow on Chromium), 2013/12/19 00:00:19]

Done.

     ],
 
     # The path to the ANGLE library.
     'angle_path': '<(DEPTH)/third_party/angle',
 
     # List of default apps to install in new profiles.  The first list contains
     # the source files as found in svn.  The second list, used only for linux,
     # contains the destination location for each of the files.  When a crx
     # is added or removed from the list, the chrome/browser/resources/
     # default_apps/external_extensions.json file must also be updated.
@@ skipping 2853 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }