Create DispatchSourceMach to run a MACH_RECV dispatch source.

sandbox/mac/BUILD.gn

 # Copyright 2014 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.
 
 component("sandbox") {
   sources = [
     "bootstrap_sandbox.cc",
     "bootstrap_sandbox.h",
+    "dispatch_source_mach.cc",
+    "dispatch_source_mach.h",
     "launchd_interception_server.cc",
     "launchd_interception_server.h",
     "mach_message_server.cc",
     "mach_message_server.h",
     "message_server.h",
     "os_compatibility.cc",
     "os_compatibility.h",
     "policy.cc",
     "policy.h",
     "xpc.h",
@@ skipping 30 matching lines @@
     "-e", rebase_path(generate_stubs_header, root_build_dir),
     "-s", generate_stubs_output_stem,
     "-p", generate_stubs_project,
   ]
   args += rebase_path(sources, root_build_dir)
 }
 
 test("sandbox_mac_unittests") {
   sources = [
     "bootstrap_sandbox_unittest.mm",
+    "dispatch_source_mach_unittest.cc",
     "policy_unittest.cc",
   ]
 
   libs = [
     "CoreFoundation.framework",
     "Foundation.framework",
   ]
 
   deps = [
     ":sandbox",
     "//base",
     "//base/test:run_all_unittests",
     "//testing/gtest",
   ]
 }