Convert DropFileSystemAccess to use ForkWithFlags.

sandbox/linux/services/credentials_unittest.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 "sandbox/linux/services/credentials.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
+#include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "sandbox/linux/tests/unit_tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace sandbox {
 
 namespace {
 
-bool DirectoryExists(const char* path) {
-  struct stat dir;
-  errno = 0;
-  int ret = stat(path, &dir);
-  return -1 != ret || ENOENT != errno;
-}
-
 bool WorkingDirectoryIsRoot() {
   char current_dir[PATH_MAX];
   char* cwd = getcwd(current_dir, sizeof(current_dir));
   PCHECK(cwd);
   if (strcmp("/", cwd)) return false;
 
   // The current directory is the root. Add a few paranoid checks.
   struct stat current;
   CHECK_EQ(0, stat(".", &current));
   struct stat parrent;
@@ skipping 92 matching lines @@
   ASSERT_FALSE(WorkingDirectoryIsRoot());
   ASSERT_EQ(0, chdir("/"));
   ASSERT_TRUE(WorkingDirectoryIsRoot());
 }
 
 SANDBOX_TEST(Credentials, DISABLE_ON_LSAN(DropFileSystemAccessIsSafe)) {
   CHECK(Credentials::DropAllCapabilities());
   // Probably missing kernel support.
   if (!Credentials::MoveToNewUserNS()) return;
   CHECK(Credentials::DropFileSystemAccess());
-  CHECK(!DirectoryExists("/proc"));
+  CHECK(!base::DirectoryExists(base::FilePath("/proc")));
   CHECK(WorkingDirectoryIsRoot());
   // We want the chroot to never have a subdirectory. A subdirectory
   // could allow a chroot escape.
   CHECK_NE(0, mkdir("/test", 0700));
 }
 
 // Check that after dropping filesystem access and dropping privileges
 // it is not possible to regain capabilities.
 SANDBOX_TEST(Credentials, DISABLE_ON_LSAN(CannotRegainPrivileges)) {
   CHECK(Credentials::DropAllCapabilities());
   // Probably missing kernel support.
   if (!Credentials::MoveToNewUserNS()) return;
   CHECK(Credentials::DropFileSystemAccess());
   CHECK(Credentials::DropAllCapabilities());
 
   // The kernel should now prevent us from regaining capabilities because we
   // are in a chroot.
   CHECK(!Credentials::SupportsNewUserNS());
   CHECK(!Credentials::MoveToNewUserNS());
 }
 
 }  // namespace.
 
 }  // namespace sandbox.