For Linux, create a ZygoteForkDelegate that uses the nacl_helper executable

chrome/nacl/nacl_launcher_thread.h

Index: chrome/nacl/nacl_launcher_thread.h
diff --git a/chrome/nacl/nacl_launcher_thread.h b/chrome/nacl/nacl_launcher_thread.h
deleted file mode 100644
index 4d709d6e082ce1a00f633589632164025d386750..0000000000000000000000000000000000000000
--- a/chrome/nacl/nacl_launcher_thread.h
+++ /dev/null
@@ -1,33 +0,0 @@
-// Copyright (c) 2011 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 CHROME_NACL_NACL_THREAD_H_
-#define CHROME_NACL_NACL_THREAD_H_
-#pragma once
-
-#include "base/native_library.h"
-#include "chrome/common/nacl_types.h"
-#include "content/common/child_thread.h"
-
-// The NaClLauncherThread class represents a background thread where
-// NaCl app gets started.
-class NaClLauncherThread : public ChildThread {
- public:
-  explicit NaClLauncherThread(bool debug);
-  virtual ~NaClLauncherThread();
-  // Returns the one NaCl thread.
-  static NaClLauncherThread* current();
-
- private:
-  virtual bool OnControlMessageReceived(const IPC::Message& msg);
-  void OnStartSelLdr(std::vector<nacl::FileDescriptor> handles,
-                     bool have_irt_file);
-
-  int debug_enabled_;
-
-  // TODO(gregoryd): do we need to override Cleanup as in PluginThread?
-  DISALLOW_COPY_AND_ASSIGN(NaClLauncherThread);
-};
-
-#endif  // CHROME_NACL_NACL_THREAD_H_