Have each SandboxedProcessLauncherDelegate maintain a zygote.

components/nacl/browser/nacl_process_host.cc

Index: components/nacl/browser/nacl_process_host.cc
diff --git a/components/nacl/browser/nacl_process_host.cc b/components/nacl/browser/nacl_process_host.cc
index 06c3c783b8ecbe368d11aeb325316e32990bbd5b..97d276d8b1ef20a94131fbc609242a5db12673ae 100644
--- a/components/nacl/browser/nacl_process_host.cc
+++ b/components/nacl/browser/nacl_process_host.cc
@@ -179,7 +179,10 @@ class NaClSandboxedProcessLauncherDelegate
     }
   }
 #elif defined(OS_POSIX)
-  bool ShouldUseZygote() override { return true; }
+  content::ZygoteHandle* GetZygote() override {
+    static content::ZygoteHandle zygote;
+    return &zygote;
+  }
   base::ScopedFD TakeIpcFd() override { return std::move(ipc_fd_); }
 #endif  // OS_WIN