Revert of Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/seccomp-bpf/syscall.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_SECCOMP_BPF_SYSCALL_H__
 #define SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__
 
 #include <signal.h>
 #include <stdint.h>
 
 #include "base/macros.h"
-#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/sandbox_export.h"
 
+// Android's signal.h doesn't define ucontext etc.
+#if defined(OS_ANDROID)
+#include "sandbox/linux/system_headers/android_ucontext.h"
+#endif
+
 namespace sandbox {
 
 // This purely static class can be used to perform system calls with some
 // low-level control.
 class SANDBOX_EXPORT Syscall {
  public:
   // InvalidCall() invokes Call() with a platform-appropriate syscall
   // number that is guaranteed to not be implemented (i.e., normally
   // returns -ENOSYS).
   // This is primarily meant to be useful for writing sandbox policy
@@ skipping 132 matching lines @@
                                     const intptr_t* args,
                                     intptr_t* err_stat);
 #endif  // defined(__mips__)
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Syscall);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__