Update from https://crrev.com/316786

sandbox/linux/services/android_arm64_ucontext.h

Index: sandbox/linux/services/android_arm64_ucontext.h
diff --git a/sandbox/linux/services/android_arm64_ucontext.h b/sandbox/linux/services/android_arm64_ucontext.h
deleted file mode 100644
index 3df0399107cd8da8858ab19ac2223305b8fb5d38..0000000000000000000000000000000000000000
--- a/sandbox/linux/services/android_arm64_ucontext.h
+++ /dev/null
@@ -1,29 +0,0 @@
-// Copyright 2014 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_SERVICES_ANDROID_ARM64_UCONTEXT_H_
-#define SANDBOX_LINUX_SERVICES_ANDROID_ARM64_UCONTEXT_H_
-
-#if !defined(__BIONIC_HAVE_UCONTEXT_T)
-#include <asm/sigcontext.h>
-#include <signal.h>
-// We also need greg_t for the sandbox, include it in this header as well.
-typedef uint64_t greg_t;
-
-struct ucontext_t {
-  unsigned long uc_flags;
-  struct ucontext* uc_link;
-  stack_t uc_stack;
-  sigset_t uc_sigmask;
-  /* glibc uses a 1024-bit sigset_t */
-  uint8_t unused[1024 / 8 - sizeof(sigset_t)];
-  /* last for future expansion */
-  struct sigcontext uc_mcontext;
-};
-
-#else
-#include <sys/ucontext.h>
-#endif  // __BIONIC_HAVE_UCONTEXT_T
-
-#endif  // SANDBOX_LINUX_SERVICES_ANDROID_ARM64_UCONTEXT_H_