Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/browser/ppapi_plugin_process_host.h

Index: content/browser/ppapi_plugin_process_host.h
diff --git a/content/browser/ppapi_plugin_process_host.h b/content/browser/ppapi_plugin_process_host.h
index 96593494cd22b12c71149d4589d168ec473647f2..85e2b64de50b1cbd7c7dbe01fae62131daac2b14 100644
--- a/content/browser/ppapi_plugin_process_host.h
+++ b/content/browser/ppapi_plugin_process_host.h
@@ -116,6 +116,11 @@ class PpapiPluginProcessHost : public BrowserChildProcessHostDelegate,
     return profile_data_directory_;
   }
 
+#if defined(OS_POSIX) && !defined(OS_ANDROID) && !defined(OS_MACOSX)
+  // Launch the zygote early in the browser startup.
+  static void EarlyZygoteLaunch();
+#endif  // defined(OS_POSIX) && !defined(OS_ANDROID) && !defined(OS_MACOSX)
+
   // The client pointer must remain valid until its callback is issued.
 
  private: