Linux: add a Credentials class to handle Linux capabilities.

sandbox/linux/sandbox_linux.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': {
     'conditions': [
       ['OS=="linux"', {
         'compile_suid_client': 1,
+        'compile_credentials': 1,
       }, {
         'compile_suid_client': 0,
+        'compile_credentials': 0,
       }],
       ['((OS=="linux" or OS=="android") and '
              '(target_arch=="ia32" or target_arch=="x64" or '
               'target_arch=="arm"))', {
         'compile_seccomp_bpf': 1,
       }, {
         'compile_seccomp_bpf': 0,
       }],
     ],
   },
@@ skipping 120 matching lines @@
     },
     { 'target_name': 'sandbox_services',
       'type': 'static_library',
       'sources': [
         'services/broker_process.cc',
         'services/broker_process.h',
       ],
       'dependencies': [
         '../base/base.gyp:base',
       ],
+      'conditions': [
+        ['compile_credentials==1', {
+          'sources': [
+            'services/credentials.cc',
+            'services/credentials.h',
+          ],
+          'dependencies': [
+            # for capabilities.cc.
+            '../build/linux/system.gyp:libcap',
+          ],
+        }],
+      ],
       'include_dirs': [
         '..',
       ],
     },
     { 'target_name': 'sandbox_services_headers',
       'type': 'none',
       'sources': [
         'services/android_arm_ucontext.h',
         'services/android_ucontext.h',
         'services/android_i386_ucontext.h',
@@ skipping 55 matching lines @@
         },
         'dependencies': [
           'sandbox_linux_jni_unittests',
         ],
         'includes': [ '../../build/apk_test.gypi' ],
         }
       ],
     }],
   ],
 }