Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/browser/ppapi_plugin_process_host.cc

Index: content/browser/ppapi_plugin_process_host.cc
diff --git a/content/browser/ppapi_plugin_process_host.cc b/content/browser/ppapi_plugin_process_host.cc
index 10719d0d393df416e7d9a7ab16edfd717cc40ef2..2edd32e12de4cd0ce52f3382362569886c0803f5 100644
--- a/content/browser/ppapi_plugin_process_host.cc
+++ b/content/browser/ppapi_plugin_process_host.cc
@@ -96,13 +96,20 @@ class PpapiPluginSandboxedProcessLauncherDelegate
   }
 
 #elif defined(OS_POSIX)
-  bool ShouldUseZygote() override {
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+  ZygoteHandle* GetZygote() override {
     const base::CommandLine& browser_command_line =
         *base::CommandLine::ForCurrentProcess();
     base::CommandLine::StringType plugin_launcher = browser_command_line
         .GetSwitchValueNative(switches::kPpapiPluginLauncher);
-    return !is_broker_ && plugin_launcher.empty();
+    if (is_broker_ || !plugin_launcher.empty())
+      return nullptr;
+
+    static ZygoteHandle zygote;
+    return &zygote;
   }
+#endif  // !defined(OS_MACOSX) && !defined(OS_ANDROID)
+
   base::ScopedFD TakeIpcFd() override { return std::move(ipc_fd_); }
 #endif  // OS_WIN