Revert of Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/linux_signal.h

-// 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.
-
-#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SIGNAL_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SIGNAL_H_
-
-// NOTE: On some toolchains, signal related ABI is incompatible with Linux's
-// (not undefined, but defined different values and in different memory
-// layouts). So, fill the gap here.
-
-#if defined(__native_client_nonsfi__)
-#if !defined(__i386__) && !defined(__arm__)
-#error "Unsupported platform"
-#endif
-
-#include <signal.h>
-
-#define LINUX_SIGBUS 7    // 10 in PNaCl toolchain.
-#define LINUX_SIGSEGV 11  // 11 in PNaCl toolchain. Defined for consistency.
-#define LINUX_SIGCHLD 17  // 20 in PNaCl toolchain.
-#define LINUX_SIGSYS 31   // 12 in PNaCl toolchain.
-
-#define LINUX_SIG_BLOCK 0    // 1 in PNaCl toolchain.
-#define LINUX_SIG_UNBLOCK 1  // 2 in PNaCl toolchain.
-
-#define LINUX_SA_SIGINFO 4           // 2 in PNaCl toolchain.
-#define LINUX_SA_NODEFER 0x40000000  // Undefined in PNaCl toolchain.
-#define LINUX_SA_RESTART 0x10000000  // Undefined in PNaCl toolchain.
-
-#define LINUX_SIG_DFL 0  // In PNaCl toolchain, unneeded cast is applied.
-
-struct LinuxSigInfo {
-  int si_signo;
-  int si_errno;
-  int si_code;
-
-  // Extra data is followed by the |si_code|. The length depends on the
-  // signal number.
-  char _sifields[1];
-};
-
-#include "sandbox/linux/system_headers/linux_ucontext.h"
-
-#else  // !defined(__native_client_nonsfi__)
-
-// Just alias the toolchain's value.
-#include <signal.h>
-
-#define LINUX_SIGBUS SIGBUS
-#define LINUX_SIGSEGV SIGSEGV
-#define LINUX_SIGCHLD SIGCHLD
-#define LINUX_SIGSYS SIGSYS
-
-#define LINUX_SIG_BLOCK SIG_BLOCK
-#define LINUX_SIG_UNBLOCK SIG_UNBLOCK
-
-#define LINUX_SA_SIGINFO SA_SIGINFO
-#define LINUX_SA_NODEFER SA_NODEFER
-#define LINUX_SA_RESTART SA_RESTART
-
-#define LINUX_SIG_DFL SIG_DFL
-
-typedef siginfo_t LinuxSigInfo;
-
-#if defined(__ANDROID__)
-// Android's signal.h doesn't define ucontext etc.
-#include "sandbox/linux/system_headers/linux_ucontext.h"
-#endif  // defined(__ANDROID__)
-
-#endif  // !defined(__native_client_nonsfi__)
-
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SIGNAL_H_