For Linux, create a ZygoteForkDelegate that uses the nacl_helper executable

chrome/common/nacl_fork_delegate_linux.h

Index: chrome/common/nacl_fork_delegate_linux.h
diff --git a/chrome/common/nacl_fork_delegate_linux.h b/chrome/common/nacl_fork_delegate_linux.h
new file mode 100644
index 0000000000000000000000000000000000000000..4d6dea2ff90d4be462469fae38c8103d246b9dcf
--- /dev/null
+++ b/chrome/common/nacl_fork_delegate_linux.h
@@ -0,0 +1,37 @@
+// 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_COMMON_NACL_FORK_DELEGATE_LINUX_H_
+#define CHROME_COMMON_NACL_FORK_DELEGATE_LINUX_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "content/common/zygote_fork_delegate_linux.h"
+
+// The NaClForkDelegate is created during Chrome linux zygote
+// initialization, and provides "fork()" functionality with
+// NaCl specific process characteristics (specifically address
+// space layout) as an alternative to forking the zygote.
+// A new delegate is passed in as an argument to ZygoteMain().
+class NaClForkDelegate : public ZygoteForkDelegate {
+ public:
+  NaClForkDelegate();
+  ~NaClForkDelegate();
+
+  virtual void Init(bool sandboxed,
+                    int browserdesc,
+                    int sandboxdesc) OVERRIDE;
+  virtual bool CanHelp(const std::string& process_type) OVERRIDE;
+  virtual pid_t Fork(const std::vector<int>& fds) OVERRIDE;
+  virtual bool AckChild(int fd,
+                        const std::string& channel_switch) OVERRIDE;
+
+ private:
+  bool ready_;
+  bool sandboxed_;
+  int fd_;
+};
+
+#endif  // CHROME_COMMON_NACL_FORK_DELEGATE_LINUX_H_