Revert of [wasm] Initial signal handler

src/trap-handler/trap-handler-internal.h

-// Copyright 2016 the V8 project 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 TRAP_HANDLER_INTERNAL_H_
-#define TRAP_HANDLER_INTERNAL_H_
-
-// This file should not be included (even transitively) by files outside of
-// src/trap-handler.
-
-#include "src/trap-handler/trap-handler.h"
-
-#include <atomic>
-
-namespace v8 {
-namespace internal {
-namespace trap_handler {
-
-// This describes a chunk of code that the signal handler will be able to handle
-// faults in. {base} points to the beginning of the chunk, and {size} is the
-// number of bytes in the code chunk. The remainder of the struct is a list of
-// protected memory access instructions and an offset to a landing pad to handle
-// faults on that instruction.
-struct CodeProtectionInfo {
-  void* base;
-  size_t size;
-  size_t num_protected_instructions;
-  ProtectedInstructionData instructions[1];
-};
-
-class MetadataLock {
-  static std::atomic_flag spinlock_;
-
- public:
-  MetadataLock();
-  ~MetadataLock();
-
-  // We'd normally use DISALLOW_COPY_AND_ASSIGN, but we're avoiding a dependency
-  // on base/macros.h
-  MetadataLock(const MetadataLock&) = delete;
-  void operator=(const MetadataLock&) = delete;
-};
-
-#if V8_TRAP_HANDLER_SUPPORTED
-void HandleSignal(int signum, siginfo_t* info, void* context);
-#endif
-
-// To enable constant time registration of handler data, we keep a free list of
-// entries in the gCodeObjects table. Each entry contains a {next_free} field,
-// which can be used to figure out where the next entry should be inserted.
-// In order to avoid having to initialize all the links to start with, we use
-// 0 to indicate that this is a fresh, never-used list entry and that therefore
-// the next entry is known to be free. If {next_entry} is greater than zero,
-// then {next_entry - 1} is the index that we should insert into next.
-struct CodeProtectionInfoListEntry {
-  CodeProtectionInfo* code_info;
-  size_t next_free;
-};
-
-extern size_t gNumCodeObjects;
-extern CodeProtectionInfoListEntry* gCodeObjects;
-
-}  // namespace trap_handler
-}  // namespace internal
-}  // namespace v8
-
-#endif  // TRAP_HANDLER_INTERNAL_H_