NaCl Linux: create NaClSandbox class

sandbox/linux/services/credentials.cc

 // Copyright (c) 2013 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 <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
@@ skipping 174 matching lines @@
       // (hence EACCES).  And if we do have this permission, then /proc won't
       // exist anyway (hence ENOENT).
       DPCHECK(errno == EACCES || errno == ENOENT)
         << "Unexpected failure when trying to open /proc/self/fd: ("
         << errno << ") " << strerror(errno);
 
       // If not available, guess false.
       return false;
     }
   }
-  CHECK_GE(proc_self_fd, 0);
+  PCHECK(0 <= proc_self_fd);
 
   // Ownership of proc_self_fd is transferred here, it must not be closed
   // or modified afterwards except via dir.
   ScopedDIR dir(fdopendir(proc_self_fd));
   CHECK(dir);
 
   struct dirent e;
   struct dirent* de;
   while (!readdir_r(dir.get(), &e, &de) && de) {
     if (strcmp(e.d_name, ".") == 0 || strcmp(e.d_name, "..") == 0) {
@@ skipping 103 matching lines @@
 }
 
 bool Credentials::DropFileSystemAccess() {
   // Chrooting to a safe empty dir will only be safe if no directory file
   // descriptor is available to the process.
   DCHECK(!HasOpenDirectory(-1));
   return ChrootToSafeEmptyDir();
 }
 
 }  // namespace sandbox.