Revert of Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/services/syscall_wrappers.h

Index: sandbox/linux/services/syscall_wrappers.h
diff --git a/sandbox/linux/services/syscall_wrappers.h b/sandbox/linux/services/syscall_wrappers.h
index 581425a367ab249a26cc74c3497fa7a5984a3b05..4558adff2bb647f212cf523cb4784eefcfe7217a 100644
--- a/sandbox/linux/services/syscall_wrappers.h
+++ b/sandbox/linux/services/syscall_wrappers.h
@@ -5,7 +5,6 @@
 #ifndef SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 #define SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 
-#include <signal.h>
 #include <stdint.h>
 #include <sys/types.h>
 
@@ -67,17 +66,6 @@
 // Some libcs do not expose a unshare wrapper.
 SANDBOX_EXPORT int sys_unshare(int flags);
 
-// Some libcs do not expose a sigprocmask. Note that oldset must be a nullptr,
-// because of some ABI gap between toolchain's and Linux's.
-SANDBOX_EXPORT int sys_sigprocmask(int how,
-                                   const sigset_t* set,
-                                   decltype(nullptr) oldset);
-
-// Some libcs do not expose a sigaction().
-SANDBOX_EXPORT int sys_sigaction(int signum,
-                                 const struct sigaction* act,
-                                 struct sigaction* oldact);
-
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_