Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/browser/zygote_host/zygote_handle_linux.cc

+// 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.
+
+#include "content/public/browser/zygote_handle_linux.h"
+
+#include "content/browser/zygote_host/zygote_communication_linux.h"
+
+namespace content {
+
+namespace zygote_handle {
+
+ZygoteHandle CreateZygote() {
+  ZygoteHandle zygote = new ZygoteCommunication();
+  zygote->Init();
+  return zygote;
+}
+
+}  // namespace zygote_handle
+
+}  // namespace content