Revert of Reland: Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/linux_ucontext.h

Index: sandbox/linux/system_headers/linux_ucontext.h
diff --git a/sandbox/linux/system_headers/linux_ucontext.h b/sandbox/linux/system_headers/linux_ucontext.h
deleted file mode 100644
index ea4d8a6c1fd58c2fa8841fb5e5609c77b7389d34..0000000000000000000000000000000000000000
--- a/sandbox/linux/system_headers/linux_ucontext.h
+++ /dev/null
@@ -1,28 +0,0 @@
-// 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.
-
-#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_UCONTEXT_H_
-
-#if defined(__ANDROID__) || defined(__native_client_nonsfi__)
-
-#if defined(__arm__)
-#include "sandbox/linux/system_headers/arm_linux_ucontext.h"
-#elif defined(__i386__)
-#include "sandbox/linux/system_headers/i386_linux_ucontext.h"
-#elif defined(__x86_64__)
-#include "sandbox/linux/system_headers/x86_64_linux_ucontext.h"
-#elif defined(__mips__)
-#include "sandbox/linux/system_headers/mips_linux_ucontext.h"
-#elif defined(__aarch64__)
-#include "sandbox/linux/system_headers/arm64_linux_ucontext.h"
-#else
-#error "No support for your architecture in Android or PNaCl header"
-#endif
-
-#else  // defined(__ANDROID__) || defined(__native_client_nonsfi__)
-#error "The header file included on non Android and non PNaCl."
-#endif  // defined(__ANDROID__) || defined(__native_client_nonsfi__)
-
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_UCONTEXT_H_