Move ForkWithFlags from sandbox/ to base/ and plug it into LaunchProcess.

base/process/launch_posix.cc

 // 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.
 
 #include "base/process/launch.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
@@ skipping 293 matching lines @@
   const sigset_t orig_sigmask = SetSignalMask(full_sigset);
 
   pid_t pid;
 #if defined(OS_LINUX)
   if (options.clone_flags) {
     // Signal handling in this function assumes the creation of a new
     // process, so we check that a thread is not being created by mistake
     // and that signal handling follows the process-creation rules.
     RAW_CHECK(
         !(options.clone_flags & (CLONE_SIGHAND | CLONE_THREAD | CLONE_VM)));
-    pid = syscall(__NR_clone, options.clone_flags, 0, 0, 0);
+
+    // We specify a null ptid and ctid.
+    RAW_CHECK(
+        !(options.clone_flags &
+          (CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID | CLONE_PARENT_SETTID)));
+
+    // Since we use waitpid, we do not support custom termination signals in the
+    // clone flags.
+    RAW_CHECK((options.clone_flags & 0xff) == 0);
+
+    pid = ForkWithFlags(options.clone_flags | SIGCHLD, nullptr, nullptr);
   } else
 #endif
   {
     pid = fork();
   }
 
   // Always restore the original signal mask in the parent.
   if (pid != 0) {
     SetSignalMask(orig_sigmask);
   }
@@ skipping 339 matching lines @@
                               std::string* output,
                               int* exit_code) {
   // Run |execve()| with the current environment and store "unlimited" data.
   GetAppOutputInternalResult result = GetAppOutputInternal(
       cl.argv(), NULL, output, std::numeric_limits<std::size_t>::max(), true,
       exit_code);
   return result == EXECUTE_SUCCESS;
 }
 
 }  // namespace base