Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/public/browser/zygote_handle_linux.h

+// Copyright 2016 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 CONTENT_PUBLIC_BROWSER_ZYGOTE_HANDLE_LINUX_H_
+#define CONTENT_PUBLIC_BROWSER_ZYGOTE_HANDLE_LINUX_H_
+
+#include <cstddef>
+
+#include "content/common/content_export.h"
+#include "content/public/common/zygote_handle.h"
+
+namespace content {
+
+// Allocates and initializes a zygote process, and returns the
+// ZygoteHandle used to communicate with it.
+CONTENT_EXPORT ZygoteHandle CreateZygote();
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_ZYGOTE_HANDLE_LINUX_H_