Revert of Reland: Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/android_arm_ucontext.h

+// 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.
+
+#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_
+
+#if !defined(__BIONIC_HAVE_UCONTEXT_T)
+#include <asm/sigcontext.h>
+
+// We also need greg_t for the sandbox, include it in this header as well.
+typedef unsigned long greg_t;
+
+//typedef unsigned long sigset_t;
+typedef struct ucontext {
+  unsigned long   uc_flags;
+  struct ucontext  *uc_link;
+  stack_t     uc_stack;
+  struct sigcontext uc_mcontext;
+  sigset_t    uc_sigmask;
+  /* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
+  int     __not_used[32 - (sizeof (sigset_t) / sizeof (int))];
+  /* Last for extensibility.  Eight byte aligned because some
+     coprocessors require eight byte alignment.  */
+  unsigned long   uc_regspace[128] __attribute__((__aligned__(8)));
+} ucontext_t;
+
+#else
+#include <sys/ucontext.h>
+#endif  // __BIONIC_HAVE_UCONTEXT_T
+
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_