Implement the V2 sandbox in the process launcher.

chrome/app/chrome_exe_main_mac.cc

 // 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.
 
 // The entry point for all Mac Chromium processes, including the outer app
 // bundle (browser) and helper app (renderer, plugin, and friends).
 
 #include <dlfcn.h>
 #include <errno.h>
 #include <libgen.h>
@@ skipping 38 matching lines @@
   char rp[MAXPATHLEN];
   if (realpath(exec_path, rp) == NULL) {
     perror("realpath");
     abort();
   }
 
   sandbox::SeatbeltExecServer server(fd_mapping);
 
   // The name of the parameter containing the executable path.
   const std::string exec_param = "EXECUTABLE_PATH";
-  // The name of the parameter containing the PID of Chrome.
-  const std::string pid_param = "CHROMIUM_PID";
 
-  if (!server.SetParameter(exec_param, rp) ||
-      !server.SetParameter(pid_param, std::to_string(getpid()))) {
+  if (!server.SetParameter(exec_param, rp)) {
     fprintf(stderr, "Failed to set up parameters for sandbox.\n");
     abort();
   }
 
-  if (server.InitializeSandbox() != 0) {
+  if (!server.InitializeSandbox()) {
     fprintf(stderr, "Failed to initialize sandbox.\n");
     abort();
   }
 
   std::vector<char*> new_argv;
-  for (int i = 1; i < argc; ++i) {
+  for (int i = 0; i < argc; ++i) {
     if (strcmp(argv[i], v2_sandbox_arg) != 0 &&
         strncmp(argv[i], fd_mapping_arg, strlen(fd_mapping_arg)) != 0) {
       new_argv.push_back(argv[i]);
     }
   }
   // Tell Chrome that the sandbox should already be enabled.
   // Note that execv() is documented to treat the argv as constants, so the
   // const_cast is safe.
   new_argv.push_back(const_cast<char*>(v2_sandbox_enabled_arg));
   new_argv.push_back(nullptr);
@@ skipping 81 matching lines @@
   if (!chrome_main) {
     fprintf(stderr, "dlsym ChromeMain: %s\n", dlerror());
     abort();
   }
   rv = chrome_main(argc, argv);
 
   // exit, don't return from main, to avoid the apparent removal of main from
   // stack backtraces under tail call optimization.
   exit(rv);
 }