fix: load window-setup in sandboxed renderer (#21416)

lib/browser/rpc-server.js

@@ -112,11 +112,15 @@ ipcMainUtils.handleSync('ELECTRON_BROWSER_SANDBOX_LOAD', async function (event)
     contentScripts = getContentScripts()
   }
 
+  const webPreferences = event.sender.getLastWebPreferences() || {}
+
   return {
     contentScripts,
     preloadScripts: await Promise.all(preloadPaths.map(path => getPreloadScript(path))),
     isRemoteModuleEnabled: isRemoteModuleEnabled(event.sender),
     isWebViewTagEnabled: guestViewManager.isWebViewTagEnabled(event.sender),
+    guestInstanceId: webPreferences.guestInstanceId,
+    openerId: webPreferences.openerId,
     process: {
       arch: process.arch,
       platform: process.platform,