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 41e337a408bb0fd76fb89ad7381449f100fd71f6..75ab51ca52ebe7a0b7e01a3d7f49782ffe5aeefe 100644
--- a/components/nacl/browser/nacl_process_host.cc
+++ b/components/nacl/browser/nacl_process_host.cc
@@ -181,7 +181,13 @@ class NaClSandboxedProcessLauncherDelegate
     }
   }
 #elif defined(OS_POSIX)
-  bool ShouldUseZygote() override { return true; }
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+  content::ZygoteHandle* GetZygote() override {
+    static content::ZygoteHandle zygote;
+    return &zygote;
+  }
+#endif  // !defined(OS_MACOSX) && !defined(OS_ANDROID)
+
   base::ScopedFD TakeIpcFd() override { return std::move(ipc_fd_); }
 #endif  // OS_WIN